The Pentagon is the headquarters of the United States Department of Defense. As a symbol of the U.S. military, the Pentagon is often used metonymically to refer to the U.S. Department of Defense. Later, it is captured by the Soviets and becomes the office of Colonel Krukov until the Epsilon Army makes their move at the beginning of the Mental Omega War and destroys it.
In Red Dawn Rising, during the Russian invasion of Washington, D.C., the Pentagon is one of the main targets of the invaders. It must be protected by the player's American forces.
In The Raven, the Pentagon has fallen under the control of the Russians. When the American rebels attack the city, it must be protected alongside the White House for 18 minutes until reinforcements can arrive.