World War I: First tank-to-tank combat, during the second Battle of Villers-Bretonneux. Three British Mark IVs meet three German A7Vs.

World War I or the First World War, also known as the Great War, was a global conflict between two coalitions: the Allies and the Central Powers. Main areas of conflict included Europe and the Middle East, as well as parts of Africa and the Asia-Pacific. There were important developments in weaponry including tanks, aircraft, artillery, machine guns, and chemical weapons. One of the deadliest conflicts in history, it resulted in an estimated 30 million military casualties, plus another 8 million civilian deaths from war-related causes and genocide. The movement of large numbers of people was a major factor in the deadly Spanish flu pandemic.

The Second Battle of Villers-Bretonneux took place from 24 to 27 April 1918, during the German spring offensive to the east of Amiens. It is notable for being the first occasion on which tanks fought against each other; it was the biggest and most successful tank action of the German army in the First World War.

The Mark IV was a British tank of the First World War. Introduced in 1917, it benefited from significant developments of the Mark I tank. The main improvements were in armour, the re-siting of the fuel tank and ease of transport. Armour was increased to resist the German armour-piercing bullet, the drivetrain was strengthened and side turrets were constructed so that they could be swung inside, enabling travel by train. A total of 1,220 Mark IVs were built: 420 "Males", 595 "Females" and 205 Tank Tenders, which made it the most numerous British tank of the war. The Mark IV was first used in mid 1917 at the Battle of Messines Ridge. It remained in British service until the end of the war, and a small number served briefly with other combatants afterwards.

The Sturmpanzerwagen A7V was a heavy tank introduced by Germany in 1918 during World War I. One hundred chassis were ordered in early 1917, ten to be finished as fighting vehicles with armoured bodies, and the remainder as Überlandwagen cargo carriers. The number to be armoured was later increased to 20. They were used in action from March to October 1918, and were the only tanks produced by Germany in World War I to be used in combat, as well as being the first operational German tank. Although various German armoured vehicle proposals were shown a modest amount of support early in the war, enthusiasm among German high command was low and they were given little funding and attention. The sudden appearance of the British Mark series of tanks causing panic amongst the German infantry led this to be reconsidered however, and development on the German tank program began.