The United States remains a key ally to South Korea and keeps a military presence to deter a second Korean War. Younger generations of South Koreans without memory of the war or poverty in its aftermath look upon the US role and continued military presence unfavorably. Governmental relations remain strong while polls of South Koreans show more unfavorable views of the US while favorable views of North Korea improved. This changed significantly in 2010 after a series of attacks by North Korea including the sinking of the South Korean navy frigate, ROKS "Cheonan".