It had to withstand floods and freezes, remain intact during a parachute drop, and stay fresh for three years without refrigeration. A combat-ready slice of pizza, a longtime dream of soldiers, is now being shipped to military bases worldwide after two decades of research. The new M.R.E. (Meal, Ready to Eat) is the handiwork of food scientists at an Army laboratory in Natick, Massachusetts. Soldiers rely on M.R.E.’s because they come in pouches and require no cooking. But troops have long complained about the bland flavor. Scientists created the pizza by developing a spongy crust and tweaking the cheese and sauce so they wouldn’t spoil. How does it taste? According to some, a bit like day-old pizza. “These were designed to be eaten when you are wet, cold, and hungry,” says David Accetta, a spokesman for the Army’s food lab. “They taste better then.”