Gen George Casey said the world remained "dangerous and unpredictable", and the Pentagon must plan for extended US combat and stability operations in both Iraq and Afghanistan that could deploy 50,000 US military personnel for a decade.
"Global trends are pushing in the wrong direction," Gen Casey said. "They fundamentally will change how the army works."
His planning envisioned combat troops in Iraq and Afghanistan for a decade as part of a sustained American commitment to fighting extremism and terrorism in the Middle East.
Gen Casey's calculations about force levels are related to his attempt to ease the brutal deployment calendar that he said would "bring the Army to its knees". His goal was, he explained, to move rotations by 2011 to one year in the battlefield and two years out for regular army troops, and one year in the battlefield and three years out for reserves. He called the current one-year-in-one-year-out cycle "unsustainable".