The Cold War ended in 1991, when the Soviet Union dissolved. Somewhat more slowly, the American military shrank, and turned into something different, unpredictable and, well, unclear.
In the 1990s, the US Navy decommissioned over 300 ships, on their way to a strength of 305 ships in 2002. In 1990, the navy was still headed for a total warship strength of 600. But, surprise, tthe crises and hot spots the navy has to deal with has actually increased. So while only about a quarter of all ships would be at sea during the Cold War, now about a third are out there. This has put more strain on sailors, as marriages fall apart and sailors got tired of the constant stress of sea duty. In response, the navy has focused on building new ships that will use 50-80 percent fewer sailors. This is not as extreme as it sounds, for commercial ships have been doing this for several decades. But no one is sure how the smaller crews will be able to handle labor intensive damage control tasks. It is only in combat that you get realistic damage control situations and navy's are always caught short when a war comes along and they discover that their damage control procedures have not kept up with peacetime changes in equipment design.
One part of the navy has not shrunk as much. During the Cold War, the army was four to five times the size of the Marine Corps, now it only about three times as large. The Marine Corps is, guaranteed by a 1950s law, to have two divisions during peacetime. Thus the marines currently account for twenty percent of America's infantry battalions, twenty percent of our fighter squadrons and seventeen percent of our attack helicopters. No wonder the army is worried about the marines being seen as our principal ground combat force. The marines have their own amphibious ships and are constantly traveling around with the fleet, ready to pounce on a hot spot before the army can get there. This is a big change from the Cold War period, when the army stood guard in Western Europe, ready to repel a possible Russian invasion. The Russian army is no longer a threat, instead an unpredictable collection of far off nations now has first call on U.S. military power. And the Marines are better organized, equipped, deployed and led for this mission.
This has left the army searching for a new mission. Unwilling to just accept their traditional role of defending the continental United States and providing large ground forces for major wars overseas, the army is attempting to reorganize to compete with the marines. Going so far as proposing the elimination of all heavy armored vehicles, the army is willing to bet their future on light infantry and untried technology. Yet the army is not taking much of a chance here, for there is no potential foe who could get a large army to North America. So the army can experiment without risk of exposing the United States to a land invasion.
The air force has been the victim of it's own success, and the disappearance of the mighty Soviet air force took away the only foe that could provide a dangerous opponent. For half a century, the air force prepared to battle thousands of Soviet warplanes for control of European air space. We built the word's best aircraft and filled them with the best trained pilots. We developed technology and tactics that were demonstrably superior, as the entire world witnessed during the 1991 Persian Gulf war. But the 1990s left the air force without a clear idea of how to deal with a murky future. So they went with what had worked before. Smart bombs, stealth and higher performance aircraft were the future. But all this stuff is expensive and it's proved difficult to find any worthy opponents to justify the escalating cost.
While there wasn't much shooting during the Cold War (although 110,000 American troops died), there was a lot of weapons development. Unlike past wars, where defense R&D slowed to a crawl when the shooting stopped, the Cold War saw a constant stream of new weapons. Many became obsolete and were replaced without ever being used in combat. The air force is not the only one stuck with a lot of expensive development projects at the end of the Cold War. But the air force has the most expensive toys, with, for example, the Stealth Bomber costing more than most navy warships. The troops can always make a case for better weapons, for that qualitative edge saves lives. But the momentum of so many 1980s era high tech projects has carried them forward even as new needs appeared. Projects like the F-22 (and similar ones for the navy and army) have powerful proponents in Congress and industry. But the navy and air force now need new transports more than higher tech combat vehicles. The army now faces more light infantry than tank divisions, yet most army R&D is still going into armored vehicles and anti-tank weapons.
While the end of the Cold War eliminated a lot of old enemies, it left a lot of old ideas, and their budgets, alive and kicking.