Drone attacks from above, top-down anti-tank missiles, and hit-and-run ambushes have quietly rewritten what a main battle tank needs to survive. The U.S. Army’s answer is the M1E3, a 60-ton next-generation tank intended to replace the 70-ton M1 Abrams that has anchored American armor since the Cold War. The new tank trades weight for survival in a different way — diesel-electric hybrid propulsion that allows silent watch mode, hemispheric Active…