The operation was a response to the recent North Korean provocations and sent a strong message of unity and determination against the continuous acts of aggression by Pyongyang, said a statement issued in Seoul by the US Naval Forces Korea (USNFK).
In the one-day drill, the allies displayed their strength with guided missile destroyer USS Spruance (DDG 111), submarines, antisubmarine helicopters and patrol aircraft.
USNFK Commander Rear Admiral Brad Cooper reaffirmed the US commitment to "remain by South Korea's side to defend against North Korea's unprovoked acts of aggression".
This new show of force by Seoul and Washington comes after the deployment of the US bombers to South Korea twice, the last time on September 21.
After the bombers flew over South Korean territory, Pyongyang accused the US of escalating tensions in the region towards a nuclear war at a time of great conflict following North Korea's fifth nuclear test on September 9.
The latest test by Pyongyang was strongly condemned by the international community, and the UN Security Council is likely to impose new sanctions on North Korea.
Pyongyang, however, ignored the criticisms and defended its nuclear and missile development on grounds of self-defence against the US.
Since the Korean War (1950-53), the US maintains a military alliance with South Korea and is committed to defend it against any possible conflict with North Korea.
