The United States, Great Britain, France, Russia, Italy, Romania, Japan and Germany, Austria-Hungary, Bulgaria and the Ottoman Empire during World War 1 all fought against each other with the new guns that they acquired while still fighting. These guns leveled the plain field with every army, but it's the wielder that makes the weapon deadly
These are the tanks that the United States used in the first World War against the German armies. There are dozens of different type of tanks they used during World War 1 and the Germans did the same by making their own tanks. Which made it level the plain field on the battlefield, but it's the driver and others in the tank that makes these iron monsters deadly.