The global defence industry has undergone serious restructuring since the end of Cold War. Military production has increasingly become concentrated in the hands of fewer but larger defence firms. The 1990s also saw mergers and acquisitions within the defence industry across the national boundaries. The resulting mega-defence firms especially in the United States dominate several sectors ranging from aerospace to shipbuilding to land systems, The European arms industry, on the other hand, has been under stress as the national markets are too small to support a heavily rationalised market.