WASHINGTON — Looking beyond America’s post-9/11 wars, Defense Secretary Chuck Hagel on Monday proposed shrinking the Army to its smallest size in 74 years, closing bases and reshaping forces to confront a “more volatile, more unpredictable” world with a more nimble military. The nation can afford a smaller military so long as it retains a technological edge and the agility to respond on short notice to crises anywhere on the globe, Hagel said.