America's first tank unit, known as the "Treat 'em Rough Boys," rushed through training and arrived in Europe in time to lead armored thrusts through Imperial German forces, assisting in the capture of thousands of Germans and miles of heavily contested territory.
The tankers were vital to the elimination of the famous St. Mihiel salient, a massive German-held bulge in the lines near the pre-war German-French border.
American forces joined the war late, participating in their first battle on Nov. 20, 1917, over three years after the war began and less than a year before it ended.
America had never attempted to create a tank before its entry into World War I. So while American G.I.s and other troops were well-supplied and fresh, most weren't combat veterans and none had any tank experience.
Into this gap rode cavalry captain George S. Patton. He lobbied American Expeditionary Force Commander Gen. John J. Pershing to allow him to establish a tank school and take command of it if the U.S. decided to create a tank unit.
Patton also pointed out that he was possibly the only American to ever launch an armored car attack, a feat he had completed in 1916 under Pershing's command in Mexico.
Pershing agreed and allowed Patton to set up the school in Langres, France. Patton quickly began taking volunteers into the school and establishing American doctrine and units.
The first-ever American tank unit consisted of the light tank units organized by Patton and heavy tanks with crews trained by England.
When it came time for the AEF to lead its first major operation, the St. Mihiel salient was the obvious target. Other allied forces had already pacified other potential targets, and the salient at St. Mihiel had severely limited French lines of communication and supply between the front and Paris since Germany had established it in 1914.
The tanks led the charge into the salient on Sept. 12 with two American light tank battalions, the 326th and the 327th, backed up by approximately three battalions worth of French light tanks and two companies worth of French-crewed heavy tanks.
Infantry units moved into battle just behind the tanks, allowing the tracked vehicles to crush barbed wire and open the way.
Per Patton's design, the tank companies were equipped with a mix of heavy guns to wipe out machine gun nests and other prepared defenses and machine guns to mow down infantry that got within their fields of fire. This mix allowed for rapid advancement except where the Germans had dug their trenches too deep and wide for the Renaults to easily cross.
The American infantry attacked the remaining resistance after the tanks passed and then took over German positions.
The light tanks, which could move at speeds faster than advancing infantry, sometimes pressed ahead and found themselves waiting for the infantry to catch up. At the village of Thiacourt, an important crossroads within the salient, tank units surrounded the village and cut off all entrances and exits while waiting for their boot-bound brethren.
While the tanks received great credit in American newspapers for their success in the AEF's first independent operation, the real story of St. Mihiel was that it was an enormously successful combined arms operations with massive amounts of artillery support, about 3,000 guns, the largest air force assembled to that date (approximately 1,500 planes), and large infantry assaults making huge contributions to victory.
Plus, the Germans had received ample warning of the AEF's pending attack and had decided not to seriously contest it. Instead, they pulled many of their units back to the Hindenburg line to the east and left only 75,000 men defending the salient against the over 260,000-man attack.
One of the prisoners, a German major and count, reportedly was even waiting with his staff and packed bags to be captured.
Of course, the first American armored offensive was not without its hiccups. The French-made Renault tanks got bogged down in deep mud. While German artillery was only able to knock out three American-crewed tanks, another 40 were lost to mud, mechanical breakdowns, and a lack of fuel at the front.
Patton continued refining American tank deployments, ordering that U.S. tanks carry fuel drums strapped to the back of the tank. At the suggestion of an unknown private, he also began equipping one tank per company as a recovery and repair tank, leading to the dedicated recovery vehicles in use today.
The tank corps went on to fight in the Meuse-Argonne offensive through the end of the war, this time with their heavy tanks there to support the infantry alongside their light armored friends. All of the tanks continued to face greater losses from terrain and mechanical breakdown than they did from enemy forces.
The greatest enemy threat to the tanks was artillery and mines, but the Germans learned to place engineering barriers such as large trenches to slow down the advance, and early anti-tank rifles took a small toll.