WASHINGTON — Defense Secretary Chuck Hagel plans to shrink the United States Army to its smallest force since before the World War II buildup and eliminate an entire class of Air Force attack jets in a new spending proposal that officials describe as the first Pentagon budget to aggressively push the military off the war footing adopted after the terror attacks of 2001. The proposal, described by several Pentagon officials on the condition of anonymity in advance of its release on Monday, takes into account the fiscal reality of government austerity and the political reality of a president who pledged...