The style of war on the land changed from World War I to be more moveable. Tanks, which were used to support infantry, changed to a primary weapon. The tank was improved in speed, armour and firepower during the war. At the start of the war, most commanders thought that using better tanks was the best way to fight enemy tanks. However, early tanks could harm armour just a little. The German idea to avoid letting tanks fight one another meant tanks facing tanks rarely happened. This was a successful tactic used in Poland and France. Ways to destroy tanks also improved. Even though vehicles became more used in the war, infantry remained the main part of the army, and most equipped like in World War I.