Operation Castration began on the 15th of October 1942 after meticulous planning by Secretary of Defence Grey Hunter, Chief of Staff Farraday and their commander in the field, Chester Nimitz.
Four US carriers, USS Enterprise, USS Yorktown, USS Wasp, and USS Long Island were sent north to the Solomons to find, engage and destroy any Japanese opposition. Several Japanese carriers had operated in the area, so confrontation was thought likely.
Action of October 15
The Japanese likely spotted the carrier force first from coast watchers or spotter planes. It was the afternoon before any combat occurred in the Solomons, and as a result of their recon the Japanese were the ones that got in the first attack. Their huge wave found the American Carriers steaming between Santa Isabel and Choiseul islands. Consisting of thirty Type 0 Fighters (Zeros), forty-nine Type 97 Carrier Attack Planes (Kates) and sixty-four Type 99 Carrier Bombers (Vals). One hundred and forty-three aircraft then tangled with the American CAP of fifty-three Wildcats.
The sixty-four Vals scored no hits and in return lost 10 of their number to flak and CAP. The Kates had more luck, one torpedo hitting USS Yorktown causing flooding and slowing her. USS Enterprise skillfully avoided at least half a dozen torpedoes shooting down almost every Kate that got close. The cruiser Indianapolis was hit by two torpedoes that Enterprise had avoided but managed to avoid sinking. The Kates' relative success was marred by their losses. Fourteen were destroyed outright during the battle, and many are likely to have been lost on their return journey, only five of the forty-nine returned undamaged. The escorting Zeros lost four of their number and managed to shoot down only one of the CAP Wildcats. USS Wasp and USS Long Island managed to escape unharmed and untargeted.
The American attack is mounted as soon as the carriers were in place. The launched a slightly smaller but better escorted raid. Thirty seven F4F-4s Wildcats escorted sixty-two SBD-3 Dauntless Dive Bombers and forty-eight TBF-1 Avengers Torpedo . Doing their best to stop the raid were sixty-one Type 0 fighters. The Wildcats, although shooting down only one Zero defended their bombers and many attacks on the Japanese task force were made. The IJN Hiyo was hit by two torpedoes and two bombs with the Dauntlesses and Avengers working in excellent co-ordination. The battleship IJN Kongo and the light carrier IJN Shoho had several AA guns knocked out with a single bomb each. Six Wildcats, six Dauntlesses and ten Avengers did not return the US task force.
Action of October 16
USS Indianapolis after the battle
USS Indianapolis began her journey home after the severe damage from the day before. Again the Japanese got in the first raid. 31 Kates, 30 Vals and 11 Zeros found the American carriers, now joined into one three carrier force. No damage was inflicted on the American carriers for the loss of two Zeros, nine Kates and seven Vals. Only a single Wildcat was shot down out of the 21 flying CAP.
The 2nd American attack. 26 Avengers, 74 Dauntlesses escorted by 23 Wildcats. 33 Zeros defend their fleet, but up to eighty of the US bombers made their attacks. For the loss of 5 Wildcats, 9 Dauntlesses and 7 Avengers a single bomb penetrated the deck of IJN Kaga. The high ratio of Avenger losses was traded by a torpedo hit on the light carrier Shoho. A single Zero was also shot down by the escorting Wildcats.
Other raids followed, with the Japanese again getting in first. Several carrier attack and bombers were noted to have come from land bases around the Shortland islands, increasing the likelihood of a Japanese carrier being sunk the previous day. Isolated Kate and Val raids were easily dealt with and a Zero sweep before their next attack resulted in four to one favouring the Americans. The afternoon carrier raid consisted of fewer than thirty bombers. However the American CAP was greatly reduced and the heroic Kates managed two torpedo strikes on USS Wasp. All the Kates suffered damage but made it away from the fray. One Zero and two Vals were lost for one Wildcat. American follow up raids all missed their attacks. Kaga, IJN Zuikaku and Kongo all too swift for the now tired Dauntless pilots. 4 Wildcats and 3 Dauntlesses did not return to their carriers.
Action of October 17
Japanese Oscars managed to shoot down a single Wildcat on CAP without taking loss early in the day. Army air force Tojos escorting Vals made an attack, but only a single Wildcat was shot down with no damage to Wasp. Passing almost within visual range of Kongo the Americans launched a raid. Five Wildcats and thirteen Avengers proved no match for Kongo and twelve Zeros. No hits were scored for the loss of seven Avengers and one Wildcat. Avengers again proving to be vulnerable to the Japanese CAPs and even the limited AA fire. Three Dauntlesses were lost in a raid on the Shortlands, sinking a cargo ship in the process. Another nine Dauntlesses were caught by ten Zeros attacking the damaged Shoho as she approached Rabaul. No hits were scored and four Dauntlesses failed to return home. A few Kates penetrate the American screen and hit Yorktown with a torpedo, however the bulkheads held and flooding was only minor.
With this the fleets moved out of range of each other and the battle concluded. Despite the last day clearly in the Japanese favour, only moderate damage was inflicted on the American carriers and at best aircraft losses were equal. The first raid by the Japanese also showed their decline in aircrew quality. In January or February of that year such an attack would have sunk all four US carriers.