ABOARD THE USS CURTIS WILBUR (AP)— On the 57th anniversary of the armistice that ended the Korean War, U.S. and South Korean ships intensified high-profile military exercises Tuesday that underscore rising tensions in a region yet to truly find peace.

The massive maneuvers, called “Invincible Sprit,” are being conducted by an armada of South Korean and U.S. ships — including the USS George Washington super carrier — in international waters off the South Korean coast.
The normally quiet patch of the East Sea has been a buzz of military activity — with helicopters dropping sonar buoys into the waters, squadrons of carrier-based F-18 fighters embarking on bombing runs and destroyers blasting their guns at unmanned aerial drones.
The exercises come just four months after a South Korean warship was sunk, allegedly by a torpedo from a North Korean submarine, in the worst attack on the South's military since the Korean War ended in a shaky truce on July 27, 1953.
North Korea has strongly denied attacking the ship in which 46 sailors died. It has threatened to retaliate over the four-day maneuvers that end on Wednesday, but senior officers aboard the U.S. ships said no North Korean military activity has been observed.
The Koreas technically remain at war because fighting ended in a truce, not a peace treaty. On Tuesday, the Koreas and the U.S. marked the anniversary of the signing of the armistice.
“Since our nation's founding, the United States has relied on our armed forces to ensure our safety and security at home, and to protect lives and liberties around the globe,” President Barack Obama said in a statement. “I call upon all Americans to observe this day with appropriate ceremonies and activities that honor our distinguished Korean War veterans.”
Gen. Walter Sharp, chief of 28,500 troops in South Korea, said the region remains tense, but stressed that the U.S. and South Korean alliance is strong.
Meanwhile, soldiers in Pyongyang, North Korea's capital, marked the anniversary of the “Fatherland Liberation War” by laying bouquets at a memorial. Residents held rallies and danced, according to the official Korean Central News Agency.
North Korean army officer Hong Sung Chol told APTN in Pyongyang the naval maneuvers were an attempt to stifle his country.
Pyongyang cites the presence of U.S. troops in South Korea as a key reason for building up its atomic weapons program. The U.S. repeatedly has said it has no intention of attacking the North.
But this week's exercises were intended to warn the North that Seoul and Washington will not tolerate acts of aggression.
The exercises involve about 20 ships, 200 aircraft and about 8,000 U.S. and South Korean sailors. At the center of the maneuvers is the USS George Washington, a floating fortress that can carry up to 70 aircraft and more than 5,000 sailors and aviators.
As fighters flew off the decks of the carrier and South Korea's defense minister toured the ship, about a half dozen destroyers stepped up their part of the drills by dropping anti-submarine bombs and firing artillery at target drones.