The Thin Red Line

U.S. Army Private Witt goes AWOL from his unit and lives among the carefree Melanesian natives in the South Pacific. He is found and imprisoned on a troop carrier by his company First Sergeant, Welsh. The men of C Company, 1st Battalion, 27th Infantry Regiment, 25th Infantry Division have been brought to Guadalcanal as reinforcements in the campaign to secure Henderson Field and seize the island from the Japanese. As they wait in a Navy transport, they contemplate their lives and the invasion. Battalion commander Lieutenant Colonel Tall talks with Brigadier General Quintard about the invasion and its importance.
C Company lands on Guadalcanal unopposed and marches to the interior of the island, encountering natives and evidence of the Japanese presence. They arrive near Hill 210, a key Japanese position. The Japanese have placed a bunker with machine guns at the top of the hill and any attempt to climb the hill will be cut down.
A brief shelling of the hill begins the next day at dawn. C Company attempts to capture the hill but is repelled by gunfire. Among the first killed is one of the platoon leaders, Second Lieutenant Whyte. During the battle, a squad led by Sergeant Keck hides behind a swell safe from enemy fire to wait for reinforcements. Keck reaches for a grenade but accidentally pulls the pin and dies in the process. Lieutenant Colonel Tall orders the company commander, Captain James Staros, to take the bunker by frontal assault, at whatever cost. Staros refuses and Tall decides to join Staros on the front line to see the situation. The Japanese resistance seems to have lessened, and Tall's opinion of Staros seems to have been sealed. Private Witt, having been assigned punitively as a stretcher bearer, asks to rejoin the company, and is allowed to do so.
A small detachment of men performs a reconnaissance mission on Tall's orders to determine the strength of the Japanese bunker. Private Bell reports there are five machine guns in the bunker. He joins another small team of men (including Witt), led by Captain John Gaff, on a flanking mission to take the bunker. The operation is a success and C Company overruns one of the last Japanese strongholds on the island. The Japanese they find are largely malnourished, dying and put up little resistance.
For their efforts the men are given a week's leave: the airfield where they are based comes under enemy artillery bombardment; Bell receives a letter from his wife informing him that she has fallen in love with someone else and wishes to divorce; Captain Staros is relieved of his command by Lieutenant Colonel Tall, who deems him too soft for the pressures of combat and suggests that he apply for reassignment and become a lawyer in the JAG in Washington. He offers to arrange a Purple Heart for Staros, to avoid the unit's name being stained by having an officer removed from command. Witt comes across the locals and notices that they have grown distant and distrustful of him and quarrel regularly with one another.
The company is sent on patrol up a river but with the inexperienced 1st Lieutenant George Band at its head. As Japanese artillery fire falls close to their positions; Band orders some men to scout upriver, with Witt volunteering to go along. They encounter an advancing Japanese column and are attacked. To buy time for Corporal Fife to go back and inform the rest of the unit, Witt draws away the Japanese but is then encircled by one of their squads, who demand that he surrender. He raises his rifle and is gunned down. The company is able to retreat safely, and Witt is later buried by Welsh and his squadmates. C Company receives a new commander, Captain Bosche and boards a waiting LCT, departing from the island.

Question: What do the Japanese place in the bunker?
Answer: machine guns