'Holly' was the US geographical rather than operational codename for Canton island of the Phoenix islands group (1941/45).
Canton island is a small atoll near the equator some 1,600 miles (2570 km) to the south-west of Pearl Harbor in the Hawaiian island group, 800 miles (1290 km) to the south of Palmyra in the Line islands group, and 960 miles (1540 km) from Makin in the Gilbert islands group. Otherwise known as 'Mild' and 'Mythology', the island is approximately triangular in shape, about 11 miles (17.75 km) long on its north-west/south-east axis and 5 miles (8 km) across its west coast. The island surrounds a lagoon with two narrow entrances on its western side, and while most of the lagoon is shallow and foul, its south-eastern part is deep enough for the operation of seaplanes. The island is flat and covered with grass and scrub, together with just a few trees, and possesses no fresh water supply. The reef is located just off the coast, except for a shelf providing an adequate anchorage for deep-water vessels off the lagoon’s south-western entrance, though in World War II this had no breakwater. The island has little in the way of resources other than small phosphate deposits and a few coconut palms.
Canton island was under joint British and US administration in 1941 under an agreement of April 1939. A seaplane base was built by Pan Am well in the 1930s, and the lagoon was dredged to facilitate seaplane operations. US Army engineers were close to completing a 5,000-ft (1525-m) runway at the time the USA entered World War II, and the 78 engineers and a handful of US Navy Consolidated PBY flying boats constituted the island’s only defence until 10 February 1942, when a 1,100-man defence force was landed, with some coast defence artillery and anti-aircraft guns, and a fighter and a light bomber squadron soon followed. Eventually the airfield was expanded to three runways.
The war largely missed Canton island, although the island was shelled three times by submarines and also by the heavy cruiser Tone early in 1943 as a diversion for the Japanese 'Ke' (i) evacuation of Guadalcanal, and was bombed on 25 March of the same year.