A Hollow Army
The United States Army emerged from the Great War with a curious new weapon and no clear idea of its purpose. The American Expeditionary Forces had used French-built Renault FT tanks, and a licensed American-made version, the M1917, began rolling off production lines just as the war ended. Yet, this nascent armored capability immediately ran into a wall of institutional inertia, doctrinal confusion, and fiscal starvation that defined the interwar period. The story of American armored doctrine between 1919 and 1940 is not one of steady progress. It is a story of a bitter internal struggle fought on three fronts: a battle between the limits of early technology and the ambitions of theory, a war between traditionalist branches and mechanization advocates, and a constant, losing fight against economic and political reality. This prolonged internal paralysis projected an image of American military weakness abroad, a perception that dangerously informed the strategic calculations of revisionist powers in Europe and Asia. The US Army of the 1920s and 1930s was, in the eyes of the world, a hollow force, its diplomatic pronouncements backed by a land army that ranked behind Portugal’s in size and was years behind in materiel and mindset.
The Constraints of Early Steel
The US Army’s first official tank, the M1917, fundamentally shackled early doctrinal thought to the concept of infantry support. A near-copy of the French Renault FT, the six-ton M1917 was a product of its time, designed to cross trenches and crush machine gun nests at a walking pace. Its specifications tell the story. A 42-horsepower Buda engine propelled the two-man vehicle to a maximum speed of about 5.5 miles per hour on roads, a speed that dropped significantly over broken ground. Its armor, a maximum of 15mm (0.6 inches) thick, could stop small arms fire and shell splinters but was vulnerable to anything larger. Armament consisted of either a 37mm M1916 cannon or a .30-caliber machine gun. The M1917 was designed to do one job: help infantrymen breach fortified lines. Its operational range was a mere 30 miles, and its two-man crew, where the commander also had to load and fire the main gun, ensured a high workload and low tactical flexibility. This technical reality directly birthed the Army’s initial armored doctrine. The National Defense Act of 1920, a piece of legislation that would haunt mechanization advocates for two decades, formally abolished the independent Tank Corps and subordinated tanks to the Chief of Infantry. This decision was not just bureaucratic, it was a codification of the M1917’s limitations. Tanks were seen as auxiliary tools, parceled out to infantry divisions to serve their needs, not as the core of a new form of warfare. The machine itself, slow and lightly armed, made it difficult for even the most forward-thinking officers to envision a role beyond the trenches of the last war.
A radical alternative appeared in the form of J. Walter Christie’s designs. His T3 Convertible Medium Tank, first built in 1931, represented a profound philosophical break. Powered by a massive 449-horsepower Liberty aircraft engine, the T3 could achieve speeds of 25 mph on tracks and a startling 40 mph on its large, rubber-tired road wheels. Its revolutionary coil spring suspension, which became known as the Christie suspension, offered unprecedented cross-country mobility. Here was a machine built for speed, exploitation, and the operational-level maneuvers that visionaries saw as the future. Yet the Army purchased only a handful for testing. Designated the T3 Medium Tank by the Infantry and the T1 Combat Car by the Cavalry, the vehicles were plagued by mechanical unreliability. They threw their tracks in hard turns, their powerful engines frequently overheated, and their thin armor, just over half an inch at its maximum, was deemed insufficient for a true combat vehicle. The Army saw an expensive, temperamental novelty, not a practical weapon. While American officials hesitated, the Soviet Union purchased Christie’s design and used it as the basis for their BT series of fast tanks, which in turn heavily influenced the legendary T-34. The world watched as American innovation was exported and perfected elsewhere, a clear signal of the US Army’s institutional inability to capitalize on its own technical creativity. This failure was a major intelligence coup for the Soviets and a source of deep concern for allied observers.
The War for Doctrine
The technological debate was a symptom of a deeper ideological conflict. The US Army’s soul was torn between the horse and the engine. The National Defense Act of 1920 created chiefs for the combat arms, including Infantry and Cavalry, giving them immense power over doctrine and procurement. This structure effectively placed the future of mechanization in the hands of its staunchest opponents. The Cavalry branch, steeped in a century of tradition, fought desperately to retain its relevance. Senior officers like Major General John K. Herr, the last Chief of Cavalry, argued that the horse possessed a cross-country mobility that no machine could match. He insisted that in mud, snow, or difficult terrain, the horse would always be superior to the fragile, fuel-hungry tank. This was not merely nostalgia, it was a fight for institutional survival. The horse defined their branch, and abandoning it meant obsolescence.
Arrayed against them were the mechanization evangelists, a small but persistent group of officers who saw the future. The central figure was Adna R. Chaffee Jr. A career cavalryman himself, Chaffee was an intellectual and a visionary who, as early as 1927, predicted that mechanized forces would dominate the next war. He championed a combined-arms concept, integrating tanks, motorized infantry, and self-propelled artillery into a fast, hard-hitting force capable of independent, decisive action. His path was a difficult one, navigating the Army’s bureaucracy. As the first commander of the experimental 1st Cavalry Regiment (Mechanized) in 1931 and later as a budget coordinator on the Army Staff, Chaffee skillfully worked to keep the concept of an armored force alive. Figures like George S. Patton Jr. embodied this internal struggle. Patton, who commanded a tank brigade in World War I, was an early proponent of armor’s potential for independent breakthrough operations. After the war, however, he returned to the Cavalry. To survive professionally, he adopted a more circumspect approach, advocating for mechanization in cavalry-friendly terms while others, like Dwight D. Eisenhower, risked their careers with more open support for an independent tank corps. This institutional battle forced proponents to resort to semantic games. To circumvent the 1920 Act’s restriction of tanks to the Infantry, the Cavalry developed “combat cars,” which were, for all intents and purposes, light tanks like the M1 and M2 Combat Car series. This internal division and terminological absurdity were clear indicators to foreign observers of an American military at war with itself, unable to forge a unified vision for modern warfare. While German officers like Heinz Guderian were building a coherent theory and force in the Panzertruppe, the US Army was hamstrung by internal rivalries, projecting an image of disunity and doctrinal confusion.
Austerity and Apathy
The final, and perhaps highest, hurdle was a crippling lack of resources. The Great Depression and a prevailing political mood of isolationism starved the military of funds. Throughout the 1920s and 1930s, military spending was a low priority for a Congress and a public wary of foreign entanglements and focused on domestic economic disaster. In 1934, the entire US Army consisted of approximately 138,000 soldiers, making it the 16th largest army in the world. Military budgets were slashed, and what little money was available was spread thin. In 1929, military spending was less than one percent of US GDP. For the nascent armored force, these budget cuts were devastating. Development was limited to a few prototypes per year. The Army produced only 15 tanks between the end of World War I and 1935. There was no money for mass production, large-scale unit training, or extensive field maneuvers. This created a vicious cycle: without a fleet of modern tanks, the Army could not properly test and validate its emerging doctrines. Without a proven doctrine, there was no compelling case to present to a skeptical Congress for the funds to build the tanks. In maneuvers, units often used trucks with signs that read “TANK” to represent armored vehicles, a practice that did not escape the notice of foreign military attachés.
This material weakness was no secret. Foreign military observers in Washington could easily report back to their capitals on the paltry state of American land forces. The image of the United States as a global power was severely undermined by the reality of its army. While President Franklin D. Roosevelt favored naval expansion, creatively using New Deal relief funds to build warships under the Vinson-Trammell Act, the Army languished. This weakness had direct diplomatic consequences. As Japan, Italy, and Germany grew more aggressive through the 1930s, they did so with the knowledge that the United States possessed a powerful navy but a negligible land army. America’s diplomatic protests against aggression lacked the credible threat of ground force intervention. This reality very likely emboldened Axis calculations that the U.S. was a “hollow giant,” unwilling and unable to project meaningful land power across the oceans. The frantic and successful expansion of the US Army’s armored forces after 1940 was a remarkable industrial and organizational achievement. Yet it was a desperate race to overcome two decades of self-inflicted paralysis. The theories of men like Chaffee were finally vindicated by the shocking success of the German Blitzkrieg in 1940, which forced the War Department to create the Armored Force in July of that year. This came only after years of internal struggle that left the nation dangerously unprepared, playing catch-up on a global stage rapidly descending into conflict.