On Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

On Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

Soldiers on Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969 get supplies, mail and copies of Stars and Stripes. (Joe Kamalick/Stars and Stripes)

Soldiers on Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969 get supplies, mail and copies of Stars and Stripes. (Joe Kamalick/Stars and Stripes)

On Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

On Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

On Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

Soldiers relax on Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

Soldiers work on defenses as a helicopter lands atop Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

On Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

On Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

From his vantage point at the radio relay station atop 3,200-foot Nui Ba Den mountain in October, 1969, 1st Lt. John Lowe of Columbus, Ohio, an artillery officer with 3rd Battalion, 22nd Infantry, 25th Infantry Division, spends his day calling in artillery strikes on the surrounding flatlands and hills. (Joe Kamalick/Stars and Stripes)

A soldier carefully steers a jeep dowm a narrow path on Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

Soldiers return from a patrol on Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

On Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

On Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

Soldiers return from a patrol on Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

Soldiers put up a fence on Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

Soldiers put up a fence on Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

A soldier takes a break on Nui Ba Den (Black Virgin Mountain), Vietnam, in 1969. (Joe Kamalick/Stars and Stripes)

NUI BA DEN MOUNTAIN, Vietnam — "They've got movement again in front of No. 6," said the GI in a perimeter bunker.

He hung up the field phone and started firing into the thick clouds that smothered this mountain top.

As the GIs launched grenades into the milky night, the crack of friendly mortars was heard exploding outside the wire where the enemy had been picked up by radar. The mortars were close, but invisible because of the cloud bank — the GIs simply call it fog — that settles on the rocky top almost every night.

It was 2 a.m. Bunker 6 had taken enemy rifle fire at midnight, but no one was hit. The GIs returned fire and kept firing sporadically throughout the night, waiting for the enemy to come up the ravine and gullies.

Their war up here is called the "waiting game."

The enemy is surely here, according to Maj. Robert Dutcher, 33, commander of the multi-service forces on Nui Ba Den, the Black Virgin mountain.

Dutcher said there are perhaps as many as 1,500 enemy troops scattered underneath the craggy hill in caves that open in crags and crevices in the brush and black granite on the mountain's sides.

"The same enemy outfit that overran this place about a year ago is back on the mountain," said Dutcher. Intelligence reports indicate, he said, that they are going to attack again soon.

"They use this mountain for the same thing we do," said Dutcher. "They get up as far as they dare to get better communications with their people across the (Cambodian) border."

"When Charlie comes up this time we will be ready for him," said Sgt. Jack Boss, 24, a bunker commander. "If we could only catch him in the wire ..."

Two men died on Bunker 7 on June 16, the last attack. The sappers came up two gullies that run on either side of the bunker and fired rocket propelled grenades at the men who were just changing watch.

"One thing you don't do, and that's panic," said Boss. "If you let him get around you then you might as well hang it up, you've had it."

Spec. 4 Dave Burlenski, 20, is one of the guards on Bunker 7. He does not have all the intelligence data that Dutcher does, but he has no illusions either.

"Oh, they'll come up again," said Burlenski. "this (area in front of Bunker 7) is the best and shortest approach to the top."

In the fog and the dark, the men on the perimeter cannot see but a few feet in front of them. They feel out the invisible terrain with M16 rifle and grenade launcher fire. It is rarely quiet here at night.

Forewarned, the men in the perimeter bunkers on top of Nui Ba Den do what they have always done — play the waiting game.