About 20 ships and submarines, 200 aircraft and 8,000 military personnel participated in the four-day "Invincible Spirit" exercises in the East Sea as a demonstration of unity and force against North Korea in reaction to the sinking of a South Korean warship in March, South Korean's Yonhap news agency reported.
"Throughout the Invincible Spirit exercises, we sent a strong warning to North Korea that its aggressive behavior won't be forgiven," Rear Adm. Kim Kyung-sik of the South's Joint Chiefs of Staff said during a briefing.
Kim said the military displayed a "formidable show of force" during the drills, adding that Seoul and Washington were "committed to together enhancing our combined defense capabilities."
South Korean military officials said the two countries reaffirmed their commitment to defeating threats posed by North Korea while the maintaining stability on the Korean Peninsula, Yonhap said.
North Korea had threatened a military response to the exercises but no unusual military activity was observed, officials said.
A multinational investigation led by South Korea determined in May that a torpedo fired by a North Korean submarine sank the warship Cheonan in the Yellow Sea, killing 46 sailors. North Korea has denied any involvement.