Israel almost didn't develop the Iron Dome that's now a core defense against incoming rockets.Ilia Yefimovich/picture alliance via Getty ImagesInternal resistance almost scuttled the development of Israel's Iron Dome air defense system.Some of the IDF brass feared that missile defense would lead to a defensive mentality.At the time, missile defense was often viewed as unfeasible, a view that's fundamentally changed.Israel today has the world's most famous — and tested — missile defenses, including the legendary Iron Dome.