Since victory in World War II, the United States Army has leveraged the nation's economic prowess to invest in increasingly heavy, technologically complex combat platforms. Our appetite for armor is clear, and comes from the belief that maximum protection, firepower, and technology, combined with the cognitive skill of the all-volunteer force, will produce the most supreme mechanized units on the battlefield. During Operations Desert Storm and Iraqi Freedom, and portions of Operation Enduring Freedom, this concept proved valid, as American Abrams tanks, Bradley infantry fighting vehicles, and later Stryker armored fighting vehicles twice devastated Saddam Hussein's army and helped seize Taliban-controlled territory in Afghanistan. These campaigns, though, will likely be markedly different than the multi-domain battlefield against a peer adversary the Army anticipates in the twenty-first century. Rather, the struggle for temporary periods of supremacy in air, sea, land, cyber, and space, coupled with the increasing vulnerability of battlefield supply lines, will prove increasingly challenging for our current armored formations, requiring a fundamental shift in the acquisition, training, and employment of our mechanized forces.