The Hill Fights

Increases in elevation on military maps are measured in meters above sea level.  A section of terrain that rises above its surroundings is generally regarded as a hill.  On military maps, hills are designated as a number that equates to the number of meters its summit rises above sea level.  For example, a hill designated 861 has a summit that rises 861 meters above sea level.  Note: Until the mid-twentieth century, the official definition of a hill was a rise in land with summits less than 1,000 feet above sea level, but this definition was abandoned.  Today, there is no official distinction between hills and mountains.

Hills aren’t uniform things, of course.  Some are natural formations, others are man-made (usually called mounds).  Forces of nature shape hills through erosion and land movement, producing such things as ridges and saddles.  And there are different kinds of hills.  A drumlin is a long hill formed by the movement of glaciers. A butte is a hill that stands alone in a flat landscape.  A tor is a rock formation on top of a hill.  A puy is a cone-shaped, volcanic hill, while a pingo is a mound of ice covered with earth.

Higher elevations allow humans to establish defenses, particularly when the hills are heavily forested or covered by thick shrub.  During the Viet Nam War, the North Vietnamese Army (NVA) and Viet Cong (VC) sought to make use of an extensive network of hills and caves to challenge US and South Vietnamese forces.  The hills in the northern regions of South Viet Nam did not stop the U. S. Marines from finding and killing them.

This is an account of the First Battle of Khe Sanh, also known as the Hill Fights.  The NVA 325C Division [1] occupied significant portions of Hills 861, 881-S(outh), and 881-N(orth), which overlooked the Khe Sanh combat base in I Corps. On 20 April 1967, operational control of Khe Sanh passed to the 3rd Marine Regiment (3rd Marines).  The 3rd Marines had just initiated OPERATION PRAIRIE IV, and although the Khe Sanh area was not included as part of the operational area, it was a territorial appendage assigned to the 3rd Marines because that regiment was in the best position to oversee and reinforce the base if necessary.

On 22nd April the 2nd Battalion, 3rd Marines (2/3) commenced Operation BEACON STAR (a search and destroy operation) in the southern portion of Quang Tri and Thua Thien provinces against elements of the VC 6th Regiment, which at the time included the 810th and 812th battalions.

On 23 April 1967 Marines of the first and third platoons of Company B, 1st Battalion, 9th Marine Regiment (B/1/9) were conducting security patrols (unrelated to Beacon Star) in the area north and east of Hill 861.  Late in the afternoon, the Bravo Company commander, Captain Michael W. Sayers [2], ordered these platoons to link up and establish a night position north of 861 in preparation for a sweep the following morning. Of interest to the Marines was a cave complex located to the northwest.

On 24 April 1967, 2ndLt Thomas G. King’s 2nd Platoon, B/1/9 led his 30 Marines and an 81mm mortar section to Hill 700, south of Hill 861.  Their mission was to provide additional fire support for a company sweep to the northwest.  Once the mortar section was in position, 1stLt Phil Sauer led four men (including a forward observer [3]) to the top of Hill 861 to establish an observation post.  As soon as the FO team entered a bamboo thicket NVA forces ambushed them.  The first Marine was instantly killed.  1stLt Sauer ordered a withdrawal, remaining behind firing at the enemy with his side arm as his men attempted to reach safety. Only the forward observer managed to escape.  This was the opening engagement of the First Battle of Khe Sanh [4].

2ndLt King, having lost radio contact [5] with the FO team, but being aware of the firefight, dispatched a rifle squad to investigate the incident.  As the squad moved forward, it came upon the FO, the team’s only survivor.  The squad returned to the area of contact to recover the other members of the team. Enemy fire kept them from retrieving the dead Marines.  The rifle squad returned to King’s mortar position.

King radioed for artillery support and then led another squad to the ambush site.  Marine artillery and air support missions pounded the hill with napalm, white phosphorous, 500-pound bombs, and gunship fire —measures that appeared to have no discernible effect on the enemy.  By the time King arrived back at the ambush site, the enemy had withdrawn, and he was able to recover two bodies.  Two other Marines were initially unaccounted for [6].

King withdrew his men to a location suitable for helicopter landing and ignited a smoke grenade marking his position and called for a medevac.  A UH-34 came in for the extraction, but no sooner had its wheels touched the deck, the whole crest of Hill 861 opened up with automatic weapons.  The chopper was hit 35 times in a matter of seconds. King’s men took cover as two UH-1E gunship escorts delivered withering fire toward the enemy positions.  As the NVA fire fell off, King’s Marines loaded the bodies aboard the helicopter, and it took off.  King and his men returned to the mortar position.

King was soon joined by Captain Sayers, who radioed the first and third platoons to sweep further east across Hill 861 and strike the NVA from the rear.  The two platoons were positioned roughly 2,000 meters (1.2 miles) northwest of their new objective.  As these two platoons turned toward their new objective, five enemy mortars dropped among them, killing one Marine and wounded several others.  The Marine advance continued [7] until halted by intense enemy fire.

After an intense engagement, with Marines running low on ammunition, they withdrew back over the crest of the hill and called for medevac assistance for their wounded comrades.  Two landing attempts were thwarted by enemy fire; the grunts took several more casualties.  Sayers ordered them to withdraw to a more secure position and dig in the night.  From the outset, Sayers realized that the NVA presence on Hill 861 was formidable.  Bravo Company Marines (through aggressive patrolling) had forced the NVA into a premature revelation of their plan to seize Khe Sanh [8].  NVA forces operating in the hills around Khe Sanh were about to receive more attention from the Marines than they had hoped for; in addition to an influx of more ground units, Hill 861 was soon receiving massive quantities of napalm and 500-pound bombs.  The NVA had broken cardinal rule number one: do not shoot at a US Marine.  Bravo Company’s losses for this day were 14 dead, 17 wounded.

The job of engaging the NVA in the hills around Khe Sanh fell to Colonel John P. Lanigan’s 3rd Marine Regiment.  Twenty-two years earlier, Lanigan had been engaged in a similar mission, one that earned him the Silver Star Medal during the Battle for Okinawa.  Prior to the incident involving King’s second platoon, Lanigan planned to replace Company B with K/3/3 on 29 April.  The events of 24th April changed that plan.

On the morning of 25 April, dense fog at Khe Sanh delayed the arrival of the 3rd Battalion, 3rd Marines (3/3), commanded by LtCol Gary Wilder.  By the time 3/3 arrived at Khe Sanh,  Captain Sayers’ Bravo Company had begun its advance on Hill 861.  Heavy fog, difficult terrain, and concentrations of enemy fire hampered the company’s progress.  Radio communications with HQ 3rd Marines was hampered by the fact that Sayers did not have 3/3’s radio frequencies.  Sayers was also convinced that the enemy was monitoring radio communications, so he sent coded messages back to his rear echelon, who passed that information to the regimental headquarters.

Shortly after arriving at Khe Sanh, Colonel Wilder began moving his battalion north to assist B/1/9. Captain Bayliss L. Spivey, Jr., commanding Kilo Company 3/3 reached the base of Hill 861 around 1500 hours and deployed his platoons on two axes: first platoon moved up along a ridgeline, followed by the company command group.  Third platoon advanced along another ridgeline on the right flank.  Kilo’s under-strength second platoon provided security for the battalion command group and a 60mm mortar section.  Spivey had his Marines positioned for an attack at 1530. Artillery check fire was in effect as the Marines closed with the enemy.

On order from Spivey, First platoon (1PLT) continued its advance through the heavy foliage on the ridgeline.  Three hundred meters from the crest, 1PLT made contact with an NVA company-size unit and encountered heavy grazing fire from well-fortified positions and mortars from reverse slope locations.  US counter-mortar and artillery was ineffective in silencing NVA mortars. 1PLT continued its attack for another 200 meters, but by 1730, the platoon had been reduced to only ten combat-effective Marines.  With darkness approaching, Spivey needed additional Marines on the line.  Irregular terrain hindered 3PLT from providing immediate assistance.  Spivey requested the release of 2PLT from 3/3 and was soon engaged in heavy combat, which continued until nightfall.  Captain Spivey ordered his Marines to dig in for the night.

Bravo Company also had a hard day.  Enemy fire prevented helicopter evacuations of Sayers’ wounded; attached Navy corpsmen were nearly exhausted.  Bravo company’s advance was limited to less than a half-mile to a position 800 meters northwest of Hill 861.

Heavy enemy resistance necessitated a call for more Marines. Captain J. E. Giles’ K/3/9 was flown to Khe Sanh from Camp Carroll.  Arriving after sundown, Giles’ company remained at Khe Sanh for the night.

The NVA launched a massive mortar assault against the 3/3 command group at 0500 on 26 April.  At the same time, NVA mortared the Khe Sanh combat base.  The shelling caused no damage at Khe Sanh, but the attack revealed a heavy NVA presence on Hill 881-S.  From information provided by Captain Sayers, Marine artillery blanketed the eastern slope of 881-S, which silenced the NVA’s recoilless rifles [9].  The mortars were more difficult to target.

K/3/9 departed Khe Sanh at 0800, arriving at the 3/3 command post (CP) at noon.  Spivey’s K/3/3 had been heavily engaged throughout the morning. NVA forces, operating from strongly fortified positions, repelled every attempt to seize the crest of the hill. By noon, Spivey’s 3PLT had taken so many casualties that it was unable to withdraw.  Wilder ordered Giles to send two platoons to help Spivey disengage and evacuate the dead and wounded.  The two companies linked up, but despite the effective use of helicopter gunships, efforts to disengage lasted until 1900.

Sayers’ Bravo company was also stopped by fierce enemy resistance.  Well-concealed enemy allowed the Marines to advance to within five meters before opening up on them.  It was a killing zone.  Sayers and his first sergeant were wounded.  NVA mortars produced additional casualties.  Nevertheless, Bravo Company gained fire superiority at noon, and the enemy withdrew.  Sayers moved his Marines to the top of a small knoll and called for medevac assistance. As the helicopters began the descent, the Marines waived them off because the aircraft were helping the NVA to pinpoint their position.  At 1445, Sayers informed Wilder that he had so many casualties he could not move his Marines further.

Colonel Wilder ordered Sayers to leave his dead and bring out his wounded.  Sayers reiterated that he could not move, even with only his wounded. Resupply was impossible.  Bravo Company had five operational radios remaining; batteries were running low.  Captain Glen Golden, commanding Battery F, 12th Marines at Khe Sanh, managed to place a ring of steel around Sayer’s position.

Wilder sent Giles and his one remaining platoon to assist Sayers.  It took Giles four hours to reach Company B.  Under the cover of darkness, heavy fog and rain, Giles and Sayers began their withdrawal.  Every man (except point and rear guard) carried stretchers of wounded and dead Marines and their equipment.  The weary Marines finally reached Wilder’s CP at 0500 on 27 April.  The few Bravo Company Marines who remained effective refused to ride trucks back to Khe Sanh.  They marched in.

Commanding the 3rd Marine Division, Major General Bruno Hochmuth [10] realized that 3/3 was an insufficient force to carry Hill 861. He shifted the Special Landing Force [11] (SLF) Battalion (2/3) under LtCol Earl R. Delong back to the 3rd Marines.  2/3 had been conducting Operation BEACON STAR at a location 16  miles north of Hue City.  The battalion was loaded on to helicopters beginning around noon on 26 April and flown to Phu Bai.  From there, the battalion was loaded aboard C-130s and dispatched to Khe Sanh.  By 1600, the 2/3 command group and letter companies E, G, and H had arrived and began their movement toward Hill 861. 2/3 set into night positions 500 meters east of Wilder’s battalion.

27 April was a day for preparations.  3/3 completed medevac operations by 1130 and moved to Khe Sanh for replacements.  Colonel Lanigan transferred M/3/9 and M/3/3 to Wilder’s battalion as relief for K/3/3 and B/1/9 —both of which were no longer capable of combat operations.  F/2/3 arrived from Phu Bai and was assigned as regimental reserve.  Battery B 12th Marines arrived at Khe Sanh at 1900 and was ready for firing missions by 2045.  Together, Batteries B and F had linked in such a manner as to allow them to perform artillery support as an artillery group.  Each battery served in direct support of an infantry battalion; two 155mm howitzers and two 4.2-inch mortars were allocated as general support of regimental operations.

Throughout 27-28th April, artillery and air delivered munitions focused on the NVA positions. The Army’s 175mm guns, situated farther east, began pouring high explosives onto Hill 861.  It was a 24-hour long onslaught of artillery and air-delivery munitions.  Snake-eye [12] munitions were used to clear away the dense vegetation so that other aircraft, armed with 750, 1,000, and 2,000-pound bombs could destroy the NVA’s well-fortified bunkers.  A preponderance of these air missions were performed by the 1st Marine Aircraft Wing (1stMAW).

Late in the afternoon of 28 April, the infantry was ready to resume their attack.  Colonel Lanigan decided on a two-battalion assault to achieve three objectives: Hill 861 was Objective 1; Hill 881-S was Objective 2; Hill 881-N was the final objective.  Delong’s 2/3 would seize Objective 1 on 28 April.  Wilder’s 3/3 would follow 2/3.  After Delong achieved his objective, Wilder’s Marines would turn west, secure the ground between 861 and 881-S, then assault Objective 2 from the northeast.  As Wilder went into the attack, Delong would consolidate Objective 1 and then move out toward 881-N, screening Wilder’s right flank, reinforcing him if necessary. After securing Objectives 1 and 2, Delong would continue on to achieve Objective 3, Hill 881-N.

Following preparatory fires, 2/3 assaulted 861 with two companies abreast.  Beyond sporadic mortar fire, there was no NVA resistance; the NVA had withdrawn.  Both companies dug in on the crest, the command group and reserve took up positions on the southern slope.  The stench of human remains permeated the entire hill. Marines discovered more than 400 mutually supporting fighting holes and 25 interlocking reinforced bunkers.

Once Delong declared 861 secure, 3/3 took up their position on the west flank of 2/3.  Wilder began his advance early the next morning. M/3/9 was the lead element.  At 1120, Mike Company’s point encountered an NVA platoon is a draw.  The company commander called for artillery and air support.  At about the same time, M/3/3 advanced to take the lead. Objective 2 was achieved at around 1915 with scant enemy contact.  3/3 dug in for the night.  Shortly after laying in their defenses, M/3/3 observed an NVA mortar team attempting to set up on Hill 881S and called in artillery.  The NVA were able to fire four rounds before being dusted by the 12th Marines.  An hour later, Marine listening posts (LPs) detected enemy movement outside their perimeter.  The company FO adjusted variable time (VT) fuzed artillery fire [13] on the enemy’s position.  Marines could hear the NVA screaming as artillery destroyed them. The Marines were not bothered for the rest of the night.

At first light on 30 April, Wilder prepared to assault 881-S and Delong moved off 861.  Delong’s mission was to clear the area on Wilder’s right flank and secure positions for the assault on Objective 3.  Company H 3/3 encountered two NVA platoons in a bunker complex.  After a particularly vicious firefight, Hotel Company backed off to evacuate casualties: 9 dead, 43 wounded.  Artillery fire was directed onto the NVA positions.  Later that day, Hotel 3/3 assaulted the bunker complex and secured it. Of this assault, the Marines concluded that the NVA regular was every bit as fanatical as the World War II Japanese Imperial Army.

The next morning, following preparatory fires, Colonel Wilder began his assault on 881-S.  He wasn’t sure where the NVA positions were, but 33 air sorties and 1,300 artillery rounds should have done some damage.  The terrain on Wilder’s approach was broken, restricted access to the ridge line, and severely constrained the maneuver of his line companies.  M/3/3 took the lead, followed by K/3/9.  By 1030, the lead platoon reached the western end of the top of the hill, having encountered only occasional small arms fire.  A second platoon moved up and together launched an assault on enemy positions.

NVA defended with automatic weapons from well-concealed bunkers and accurate sniper fire.  Thirty mortar rounds fell on these Marines.  They were stuck —unable to advance or withdraw.  NVA infantry from bypassed (unseen) bunkers blocked their way out.  K Company and the 3rd platoon of Mike Company advanced into the savage battle.  UH-1E gunships and attack aircraft streaked in dropping bombs within 50 meters of the Marine line.  Wilder ordered his Marines to disengage and pull back off the hill.  It took the Marines several hours to disentangle themselves.  They brought out their wounded but could not evacuate the dead.  Forty-three Marines were killed, 109 were wounded. Mike Company was rendered ineffective.

Fox Company 2/3 was brought in from reserve.  With the reserve committed and no other to replace it, General Hochmuth committed another rifle company to the hill fight: Company E 2/9 was flown in to Khe Sanh.  Marine artillery and aircraft reengaged Hill 881-S.

Wilder was ready to resume his attack on the morning of 2 May.  M/3/9 and K/3/9 led off in that order.  By 1420, the Marines had secured the hill, having encountered only sporadic sniper fire.  Wilder established his CP on 881-S and dug in for the night with two assault companies. F/2/9, the most recent arrival, took up a position on the intermediate objective.

The NVA had prepared around 250 bunkers on Hill 881-S.  After four days of heavy air strikes and artillery fire, 50 of these remained. The bunkers were wired for communications and arranged with interlocking fields of fire.  The extent of these bunkers surprised the Marines, but their discovery alerted Colonel Delong of what he might expect on 881-N.

Since 28 April, Delong’s Marines had been sweeping the area northwest of the hill, carefully checking its ravines and ridgelines.  By the morning of 2 May, Delong was ready to begin his objective.  Echo Company 2/3 assaulted the hill from the south; Golf 2/3 moved in from the east.  Hotel 2/3 was in reserve between the maneuver companies.  Golf made contact almost immediately and after a brief firefight, moved back and called in artillery.  After the artillery was lifted, Golf moved forward again, encountering automatic weapons fire and mortars.  Additional supporting arms silenced the enemy.  Hotel Company moved into position to support Golf and also came under mortar fire, which ceased when Golf called in for additional artillery.

Echo Company had almost battled its way to the crest of the hill when a fierce rain squall lashed at the hills.  Delong, realizing that control of his men under these circumstances would be impossible, pulled the battalion back to a more defensible position and ordered his Marines to dig in for the night.  Early in the morning of 3 May, the NVA launched a strong counter-attack.  Echo Company set in on a small hill 500 meters south of Hill 881-N received small arms fire and incoming mortars.  This was followed by a two-company NVA assault.  The engagement soon devolved into hand-to-hand combat with the NVA penetrating the line on the northeast quarter. The NVA either killed or wounded all the Marines in this area.  They then moved into a tree line in the middle of the company position and reoccupied bunkers that the engineers had yet to destroy.

About ten minutes after the initial attack, First Lieutenant Frank Izenour (whose platoon held the western section of the perimeter), received orders to take a squad of Marines and seal off the penetration. With the second squad in tow, Izenour moved forward but was immediately taken under fire by two machine gun positions; several of his men were hit.  Izenour called for reinforcements.

Captain Alfred Lyon did not want to weaken the 1st platoon further, so he organized eleven engineers and sent them into the fight.  Both squads took positions on the left edge of the penetration and fired into the enemy’s flank.  With the help of artillery and on-call gunships, the Marines stalled the NVA attack, but Izenour still did not have sufficient strength to drive out two companies of NVA regulars.  A flare ship arrived and transformed the dark of night into day.  From 881-S, the Marines of 3/3 could see about 200 NVA soldiers moving toward Echo Company from the west.  106mm recoilless rifles were quickly positioned; 100 rounds were fired into the enemy’s flank, which broke up the assault.  Additional artillery pounded the NVA as they withdrew.

By first light, the Marines had shattered the NVA attack, but some enemy soldiers remained inside the company perimeter.  At 0700, Fox 2/3 moved into the line and one platoon was quickly transferred by helicopter to Echo Company’s position.  These Marines immediately attacked the southern edge of the penetration.  Delong ordered Hotel Company to close in on the enemy’s rear.  Echo and Hotel companies finally managed to seal the breach. After a short rest, Hotel Company began the difficult task of eliminating NVA in the bunkers and tree line. Bitter close-quarters fighting continued until 1500 when the company commander declared all bunkers cleared of the enemy.  The NVA had fought to the last man.  Company E lost 27 Marines KIA with 84 wounded.  NVA dead covered the battle area.  Only three prisoners were taken, these all admitting that another attack was scheduled for the night of 4 May.

Despite Delong’s preparations for that night, the expected attack never came.  Instead, an NVA company attacked the Special Forces Camp at Lang Vei.  The attack had no effect on The Hill Fight, but it was a tactical victory for the NVA, who quickly penetrated the camp’s defenses and killed everyone they could find, including the Special Forces Detachment Commander and his Executive Officer. The NVA then began destroying vital equipment.  Despite artillery fire from the Marines at Khe Sanh, the NVA withdrew with only light casualties.  South Vietnamese irregulars at Lang Vei were destroyed: 20 killed, 39 missing.

Given the attack at Lang Vei, General Hochmuth ordered Company C, 1st Battalion, 26th Marines flown in from Phu Bai to bolster security at Khe Sanh.  On 5 May, Delong’s Marines advanced toward the final objective. While organizing his Marines for the assault, artillery and air strikes dropped tons of munitions on Hill 881-N. E/2/3 and F/2/3 took the lead, meeting steadily increasing resistance.  The Marines halted their advance on several occasions while additional artillery could soften up the enemy’s opposition.  Echo Company established a base of fire while Fox Company resumed the advance and Golf Company made an envelopment maneuver.  By now, the only resistance encountered was sporadic sniper fire.  2/3 achieved the objective at 1445.

For the next three days, Marines conducted sweeps of the area, searching the hills for any additional NVA presence.  Engineers destroyed all remaining bunkers.  Marine air attacked suspected enemy positions to the north and west. Air observers reported enemy troops moving toward the northwest, indicating that the 325C Division was withdrawing toward Laos and North Vietnam.

During The Hill Fight, 1stMAW flew more than 1,100 sorties, expended 1,900 tons of ordnance.  USAF B-52s made 23 air strikes against enemy concentrations.  Combined Marine and Army artillery fired 25,000 rounds.  NVA casualties between 24 April and 11 May stood at 940 confirmed killed. Of the Marines, 155 were killed in action, 423 suffered combat wounds.

Sources:

1. Telfer, G. L. and others. U. S. Marines in Viet Nam: Fighting the North Vietnamese.  History & Museums Division, HQ U. S. Marine Corps, Washington, D. C.  1984
2. “Arrow of Death.” Time Magazine, 12 May 1967

Endnotes:

[1] The 325th Infantry Division was first formed in 1951 from independent units in Thua Thien Province, one of six “iron and steel” divisions of the Viet Minh.  The 325th Division remains part of the Army of Viet Nam.

[2] Sayers was responsible for the security of the Khe Sanh combat base.  Conducting security patrols in the surrounding area was part of that responsibility.

[3] Forward observers are trained to direct artillery and close air support to enemy positions within the battle space.

[4] Communist gunners held their fire until Marines were at near point-blank distance from concealed machine gun positions and made liberal use of their 82mm mortars, the blasting radius of which was about 40 meters.

[5] Line of sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation.  The means that radio waves travel in a direct path from source to receiver. Mountainous terrain interrupts these signals.

[6] The bodies of the two missing Marines were later found.  The NVA had decapitated them.

[7] Advancing toward the enemy is a standard defense against mortar attack.

[8] The NVA plan for Khe Sanh was a rehash of the one they had used against the French at Dien Bien Phu in 1954.  First, a major effort to build up troops and supplies; second, isolation of Khe Sanh by targeting helicopters and cutting the main supply route; third, launch diversionary assaults at Con Thien, Dong Ha, Gio Linh, Phu Bai, and Lang Vei.

[9] Recoilless rifles provide a lightweight artillery capability to forward units.  It fires a 105mm shell that has a destructive effect on troops operating in mountainous areas where heavy artillery is much too cumbersome.

[10] MajGen Hochmuth was killed on 14 November 1967 when his helicopter exploded mid-air.  Hochmuth was the most senior US military officer killed in the Viet Nam War.  He was succeeded in command by BrigGen Louis Metzger, the Assistant Division Commander, previously Commanding General, 9thMAB.

[11] The special landing forces belonged to the 9th Marine Amphibious Brigade as part of a naval task force, designated Task Force 79.  When the SLF went ashore, operational control of the battalion landing teams (BLTs) were transferred to the senior operational commander ashore.

[12] Snake-eye refers to the high drag fin system of the Mk-82 bomb, but the fin configuration was also used on all Mk-8 series munitions.  The Mk-82 is an unguided, low drag, general purpose bomb.  In low-level operations, it is possible for the delivery aircraft to receive damage from the blast and fragmentation effects of the bomb because the aircraft and bomb arrive at the target very close to the same time.  This was the reason for the high-drag tail fin configuration.

[13] VT fuze detonates an artillery round several meters above the ground, which increases fragmentation and kill radius.  Air bursts are especially effective against troops in the open or in unprotected positions, such as fox holes or open trenches.