When the Army of the Democratic People’s Republic of Korea (DPRK, better known as North Korea) swept across the border along the 38th parallel on June 25, 1950, both the Republic of Korea (ROK) Army and its American allies (in fact only advisers and a small garrison) were taken completely by surprise. The first four days saw the North Korean army make very rapid progress against inferior forces lacking tanks, armor, and aircraft. By June 27, the government of South Korea under President Syngman Rhee was heading south to Taejon to avoid capture, and soon after, a headlong retreat began. The front did not stabilize until a defensive perimeter was established around the port of Pusan, far to the south.

To the North Korean army commanders, victory must have seemed a foregone conclusion, but they reckoned without sea power.

To the North Korean army commanders, victory must have seemed a foregone conclusion, but they reckoned without sea power. The Republic of Korea Navy (ROKN) was a negligible collection of some 40 small vessels, too weak to resist the DPRK Navy, itself mustering only 50 ships in all. But the geography of the Korean peninsula made communications particularly vulnerable to pressure from the sea, with road and rail links largely avoiding the mountainous interior, and great reliance placed on coastal shipping. The United States and its principal allies Great Britain, Australia, Canada, and New Zealand, maintained substantial forces in the region, and the U.S. Navy’s 7th Fleet had the inestimable advantage of major bases in Japan. Last but not least, the framework of a joint command already existed, with Gen. Douglas MacArthur commanding U.S. forces in Japan, although all three services still had their own headquarters. Prompt diplomatic and military action by Washington turned the conflict into a United Nations (U.N.)-backed “police action” to halt what was perceived to be an invasion not only supported but instigated by the Soviet Union.

President Harry S Truman ordered U.S. sea and air forces to support ROK forces, sending the 7th Fleet to the Formosa Straits to checkmate any attempt by China to threaten Taiwan. Adm. Arthur W. Radford, commander in chief of the Pacific Fleet, was ordered to form a new task force in the Western Pacific (TF 77). By July 7, MacArthur was given a second “hat” as commander in chief of U.N. forces, and a unified command came into existence. The British government as early as June 27 had signified its willingness to do everything in its power to support “other U.N. forces” in preventing aggression against South Korea. In practice, the U.N. made no attempt to direct military operations, handing over responsibility to the U.S. president, his Joint Chiefs of Staff, and MacArthur.

The British government as early as June 27 had signified its willingness to do everything in its power to support “other U.N. forces” in preventing aggression against South Korea. In practice, the U.N. made no attempt to direct military operations, handing over responsibility to the U.S. president, his Joint Chiefs of Staff, and MacArthur.

In July, the escort carrier USS Sicily (CVE 118) left San Diego, Calif., ferrying aircraft to Japan, while the fleet carriers Philippine Sea (CV 47) and Valley Forge (CV 45) were soon in Korean waters. The Royal Navy light fleet carrier HMS Triumph had left Ominato in Japan the day before the North Korean invasion, but was ordered to return to Japan, while the second-in-command of the Far East Fleet, Rear Adm. Sir William G. Andrewes, moved his flagship, the cruiser HMS Belfast, from northern Japan to Yokosuka. On June 28, the Triumph, the cruiser HMS Jamaica, and two destroyers joined the Australian frigate HMAS Shoalhaven and an oiler at Kure.

The presence of the carriers proved a godsend to the hard-pressed ground forces, because the ground war was still too fluid to permit the construction of large airfields. Bombers based in Japan pounded strategic targets, but the precise tactical support needed by ground troops could only be provided at short notice by naval aircraft. The U.S. Navy reactivated three Essex-class carriers, and by the fall, the battleship Missouri (BB 63) was to be joined by her recommissioned sisters Iowa (BB 61) and New Jersey (BB 62) to provide massive fire support with their 16-inch guns. The solitary Royal Navy carrier Triumph was relieved by her sister Theseus and later by the Glory and Ocean. The Royal Australian Navy contributed HMAS Sydney, yet another example of the versatile 14,000-ton British Colossus design. The British carriers suffered from a shortage of suitable aircraft, the Seafire proving yet again that it wasn’t sufficiently robust for carrier landings. The replacement of the Seafires and the Firefly 1s by longer-ranged Sea Furies and Firefly 5s improved efficiency noticeably.

Mines were a great threat, for the North Koreans had ample supplies of Soviet mines, both contact and influence types, and showed great ingenuity in trying to deny coastal waters to U.N. ships. Junks laid minefields at night, and several warships were damaged. The Wonsan landings were seriously jeopardized when it was discovered that the latest Soviet magnetic mines could not be swept by World War II vintage non-magnetic minesweepers.