Trench warfare
Trench warfare occurred when a revolution in firepower was not matched by similar advances in mobility, resulting in a grueling form of warfare in which the defender held the advantage. On the Western Front in 1914–1918, both sides constructed elaborate trench, underground, and dugout systems opposing each other along a front, protected from assault by barbed wire, mines, camouflaged trapping pits, and other obstacles. The area between opposing trench lines (known as "no man's land") was fully exposed to artillery fire from both sides. Attacks, even if successful, often sustained severe casualties.
7th Cavalry Brigade (United States)
After the brutal trench warfare of World War I, the United States was looking for new ways to engage in armed conflict. As the German Army invaded France, Belgium, Luxembourg, and the Netherlands, the United States military hierarchy realized that an armored division was essential for a modern army. While training outside of Alexandria, Louisiana, the commanders of the 7th Cavalry Brigade met in a high school basement to discuss the creation of an American armored division. Major General Frank M. Andrews, Generals Adna R. Chaffee and Bruce Magruder, and Colonel George S. Patton Jr. agreed to recommend to Washington that the U.S. Army establish its first tank division.