WASHINGTON—The Army took a major step to prepare for wars of the future in January when it established a new battalion in Europe to master the art of fighting with drones and ground robots.A U.S. Army servicemember using a small unmanned aircrafts system, or sUAS, controller.The idea was to learn the lessons of the conflict in Ukraine that has been raging on the North Atlantic Treaty Organization’s doorstep and develop cutting-edge military systems and tactics to counter the Russian threat.But the much touted drone assault battalion is being phased out. After participating in a major exercise in Germany in August…