This event has always bothered me, and partly illustrates why there were such high casualties among Machine Gunners. The squad had been informed by local citizens that a party of North Koreans had been seen entering this tunnel, so the Marines were only making sure they had gone on through.
Truman and his cabinet had virtually turned the United States Marine Corps into a police force for the Navy. The Pusan Perimeter was saved and the assault at Inchon possible only because the Reserves were called up, once Truman realized his mistake. These Marines might have been in the Reserves, driving buses or pumping gas only two months before being thrown into an infantry company and facing and defeating NK veterans here in Seoul. But they did defeat them, and continued to face and defeat them at the Han and at Seoul. And they went on to face 12 Chinese divisions at Chosen.
Still, the M1919A4 Light Machine Gun although slightly off-set from the tunnel axis, is vulnerable to whatever firepower the enemy left to delay pursuit. The Marine throwing a grenade into the entrance should have thrown it before any troops exposed themselves to fire from within.
