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Plot

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A Marine patrol stops at Firebase Gloria at the start of the Tet Offensive during the Vietnam war. With the firebase attacked, the patrol remains to help defend it. The Marines barely hold off the VC (Viet Cong), but in the end, hold the base. They're subsequently forced to abandon it, having lost too many men in the process of defending it.

While the movie focuses primarily on the defense of the base, it is set against the backdrop of the larger events of the Tet offensive in 1968.

Major Subplot

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The VC commander, attacks again and again. At the end of the movie, he discovers that it was never his mission to "win" the battle, but rather to lead his men to their deaths, so that the North Vietnam Army could take over the war. As the film's narrator, R. Lee Ermey notes in the epilogue that the Viet Cong were decimated by the Tet Offensive and never functioned again as a significant military force for the remaining seven years of the war.