Part VII: Operation Powder Horn
By early February 1943 it was clear that operation Popcorn had been a complete success. Darwin’s reconstituted air defenses had prevented damage from most of the subsequent Japanese air raids, and what damage was being caused was paid for disproportionately with Japanese aircraft losses. Darwin ability to function as an advanced submarine base was being maintained and only a large commitment of scarce IJN resources was likely to change that.
In Burma, the allies had advanced as far as Akyab but ground activities in this theater had ground to a halt due to the inability to provide adequate supplies to the troops there. Overland supply capacity was insufficient and land based aircraft from the numerous Japanese bases were mauling convoys delivering supplies. The British government had been lobbying hard for sea based air cover for these convoys, and the success of Popcorn reinforced their case. Against the wishes of CINCPAC, the Saratoga, Enterprise and Hornet were transferred to the Indian Ocean during a lull in the Solomons campaign.
Per OPSEC requirements the code name for this operation was randomly selected to be “Powder Horn”, but its unofficial name was “Popcorn II”. The success of Popcorn proved to be a liability for Powder Horn since many of the measures that had been adopted in the earlier operations were discarded due to complacency. The CVE escorts that had provided close air cover for the transports were left at Noumea due to the additional transit time that the slower jeep carriers would require. And the three fleet carriers’ air groups were not shuffled to provide enlarged fighter complements. This latter decision was due to retain sufficient striking power to neutralize air fields or to engage the IJN should the opportunity arise (at least two Japanese CVs were know to be operational but their location was unkown). Unlike Darwin, the British would be able to provide significant land based fighter support throughout the operation since fresh squadrons based at Calcutta could be rotated to Chittagong and Cox’s Bazar to provide air cover over Akyab.
The three US carriers and their escorts completed the transit to Ceylon, hugging th northern Australian coast to avoid air attacks from the nearby occupied islands. A few days were spent in Colombo repairing overworked machinery and then the CV covering force rendezvoused with the transport force at Madras to make the trip to Akyab. The first Japanese strikes did not begin until the combined force was within British fighter cover: two raids totaling 114 Oscars, 22 Lilys, and 9 Sonias attacked the transports with no hits being scored. 12 Oscars, 7 Lilys, and 6 Sonias were shot down in exchange for 3 Wildcats and a Hurricane [This was based on the combat report. Japanese losses reflected in the Intel screen were about double these]. Similar results were obtained on the second and third days but by this point operational fighter strength on the carriers was down to one-third of normal. The bulk of the CAP support was now being provided from Cox’s Bazar which still had 81 operational fighters. Supplies were flowing to the troops at Akyab but the base still had not accumulated any surplus.
By the fifth day the CAP over Akyab was beginning to weaken and bombers were getting through. An xAK was hit twice and sunk but Japanese air losses remained high. The size of the strikes was nonetheless growing as the Japanese shifted more combat aircraft to bases within range of the targets. Allied fighters were maintaining a 4:1 kill ratio, Akyab engineers had built a small [level 1] port facility, and a small supply surplus had finally been accumulated [1,114]. With supplies now available, 31 Hurricanes were transferred to the Akyab airfields to provide more effective land based air cover.
No air attacks were made against Akyab on day six of Powder Horn, but days seven through nine saw heavy attacks with large numbers of escorts. Total sorties were 22 Zeros, 203 Oscars, 92 Nates, 45 Lilys, 6 Sonias, and 32 Sallys vs. 459 CAP sorties. No hits were scored. Akyab supplies had built up [to 26,531] and the transports had two days of unloading left. Engineers had managed to expand Akyab’s primitive port facilities further and this accelerated the supply transfers to shore. Smaller raids over the next three days seemed to indicate that Japanese air strength was waning; the only shipping damage suffered was a bomb hit by a lone search plane that had eluded CAP cover. On day 13 the carriers and transports withdrew and began the return transit to Colombo and Madras respectively.
On 3/26/43, the transports began reloading at Madras for a second supply run to Akyab. The carriers took on replacement aircraft at Colombo that had been ferried in in advance of the operation, and aircraft mechanics labored to return damaged air frames to service. Although no shipping targets had been available, the fighter pilots were gaining combat experience even more rapidly than they had in the Solomons fighting and US naval commanders’ objections to investing scarce carriers to this operation were softening. Their resolve was to harden again two days after the carriers and transports returned to Akyab. On 4/3/43, the pilot of a Sally that had been severely damaged by AA fire managed to crash his flaming plane onto the aft section of the Hornet’s flight deck. Casualties were heavy and the Hornet’s airborne CAP and ASW patrol aircraft had to divert to other carriers or air bases. Although the ship was in no danger of sinking [Sys 24, Flot 30, Eng 9] it was clear that carrier support of Powder Horn had been reduced at least temporarily by a third. But the British had promised to give damaged US carriers in Colombo’s shipyard and there was every expectation that the Hornet could be repaired and returned to service in a month or two.
The weaknesses in Powder Horn became evident when the ships withdrew after unloading. As soon as the carriers were outside of effective land based support, a strike by Betties and Zeros from Port Blair put two torpedoes into the damaged Hornet. The wounded carrier was in grave danger [Sys 61, Flot 40, Eng 32, Fire 4]; the risk of another successful air strike against her the next day influenced the task force commander to order best speed away from the Japanese air base and toward the safety of Colombo. But the increased hydrodynamic loads on the Hornet’s weakened bulkheads caused more failures and flooding and efforts to keep the ship afloat finally failed three days later.
With only two carriers left to support Akyab’s continuing supply convoy needs CINCPAC requested permission to suspend Powder Horn until all available CVEs and possibly an additional fleet carrier could be transferred but British government pressure again won out and ADM Kimmel was directed to continue the operation with the assets available. By concentrating bombing raids on the nearby Japanese airfields beginning a few days before the expected departure of the transport ships, a repeat of the Hornet disaster was avoided. Hugging the Burmese and Indian coasts until out of torpedo bomber range of Port Blair also helped although this added to the return transit time. Powder Horn did achieve its objective of restarting the stalled British and Indian drive through Burma.