U.S. military commanders have requested that the Pentagon keep more combat forces stationed in Europe to respond to potential threats, including a more aggressive Russia, senior military officials said. Plans to reduce the number of troops based in Europe will leave commanders with too few soldiers to protect and train with allies on the continent and to stand ready for deployment to trouble zones elsewhere, such as Iraq and Afghanistan, said General David McKiernan, head of Army forces in Europe. “In this era of persistent conflict, we have some fault lines that are there in the European Command [responsibility area] that we have to pay attention to,” McKiernan said Thursday in Washington. “We don't know what's going to happen in terms of a resurgent Russia.” European Command, which includes about 95,000 U.S. personnel, supports NATO and since 2001 has provided troops to Afghanistan and then Iraq. Both of those conflicts are managed by U.S. Central Command. Recent activities by the Russian military have led some defense officials and military officers to reconsider plans to reduce the U.S. military presence in Europe. Amid strained relations between Washington and Moscow over U.S. missile-defense plans, Russia has issued a series of statements about building its military power and has resumed long-range bomber missions to U.S.- and NATO-patrolled areas. McKiernan said some Russian activities of concern to military leaders included the resumption of long-range reconnaissance flights and weapons sales to countries unfriendly to the United States. He said other worrisome situations would be Russian involvement in border conflicts and military action outside its territory.