Sierra Bombardment Group
The Sierra Bombardment Group was a provisional United States Army Air Corps organization formed immediately after the attack on Pearl Harbor.
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Overview
The Sierra Bombardment Group was a short-lived provisional organization of the United States Army Air Corps created on 8 December 1941 at Minter Field, California, in the immediate aftermath of the Japanese attack on Pearl Harbor. It was not a commercial brand but a wartime military formation assembled from aircraft and aircrews that had been preparing to reinforce American forces in the Philippines. The group brought together two different bomber elements. Its heavy-bomber component consisted of ten B-17E Flying Fortresses and personnel formerly associated with the 7th Bombardment Group's 32d and 427th Bombardment Squadrons. Its medium-bomber component consisted of thirty-five B-25 Mitchells assigned from the 17th Bombardment Group of the Second Air Force at Pendleton Army Airfield, Oregon. The provisional arrangement reflected the rapidly changing strategic situation in the Pacific: aircraft intended for overseas deployment were instead redirected to continental defense and emergency reinforcement missions. The B-17 element briefly conducted coastal patrols from Muroc Army Airfield, California. As the situation in the Philippines deteriorated, the aircraft began moving westward. On 17 December 1941 they departed through Hawaii, where the aircraft were temporarily committed to defensive reconnaissance rather than immediately continuing to the Philippines. Three B-17s were eventually released for onward movement toward Mindanao, but they were diverted to Java in the Netherlands East Indies. There they joined evacuated elements of the 19th Bombardment Group operating from Singosari Airfield. The remaining B-17s stayed at Hickam Field until 10 January 1942, then traveled toward Australia through Christmas Island, Canton Island, and Fiji. After a delay in Fiji, they reached Townsville, Queensland, and were absorbed as replacements by the 19th Bombardment Group. The B-25 component remained in Oregon and performed coastal antisubmarine patrols along the Pacific Northwest coast. The aircraft lacked radar and comparable submarine-detection equipment, so crews relied mainly on visual observation. Reports of suspected enemy submarines sometimes involved whales, logs, or other objects. A crew claimed to have bombed and sunk a submarine near the mouth of the Columbia River on 24 December 1941, but no Japanese submarine was actually sunk off the American West Coast during the Second World War. The Sierra Bombardment Group was discontinued in early February 1942 after its aircraft and personnel had been reassigned to operational formations. Its significance lies in illustrating the improvised organization and rapid redeployment of American air units during the opening weeks of the Pacific War.
History
The Sierra Bombardment Group emerged from the emergency reorganization of American air assets following Pearl Harbor. On 8 December 1941, one day after the attack, the United States Army Air Corps established the provisional unit at Minter Field in California. Its personnel and aircraft had originally been associated with forces preparing for movement to the Philippines, but the Japanese offensive made those plans uncertain and created an immediate need for defensive patrols and reinforcements. The group had two principal components. Ten B-17E Flying Fortresses and their crews came from the 7th Bombardment Group's 32d and 427th Bombardment Squadrons. Thirty-five B-25 Mitchell medium bombers came from the 17th Bombardment Group of the Second Air Force at Pendleton Army Airfield in Oregon. Although organized under one provisional headquarters, these components soon followed different operational paths. The B-17s first performed coastal patrols from Muroc Army Airfield, California. As the Japanese campaign in the Philippines advanced, the Army Air Corps attempted to move the heavy bombers westward. They left for Hawaii on 17 December 1941. At Hickam Field, however, the aircraft were used for defensive reconnaissance. Three were released for a proposed movement to Mindanao, but they were diverted to Java in the Netherlands East Indies, where they joined evacuated elements of the 19th Bombardment Group operating from Singosari Airfield. The remaining B-17s departed Hickam on 10 January 1942. Their route crossed Christmas Island, Canton Island, and Fiji before reaching Australia. The aircraft spent almost a week in Fiji while authorities dealt with Vichy French guerrilla activity, then continued to Townsville, Queensland. There, the B-17s and their crews were assigned to the 19th Bombardment Group as replacements. This reassignment effectively removed the heavy-bomber element from the provisional Sierra organization. The B-25s stayed in Oregon and carried out coastal antisubmarine patrols along the Northwest Pacific Coast. Their equipment was poorly suited to systematic submarine detection: the aircraft lacked radar and similar specialized devices, leaving crews dependent largely on visual sightings. Aircrews sometimes interpreted whales, logs, and other floating objects as enemy submarines. On 24 December 1941, one B-25 crew reported bombing and sinking a submarine near the mouth of the Columbia River. The claim was not supported by later historical evidence; no Japanese submarine was sunk off the United States West Coast during the war. By early February 1942, the Sierra Bombardment Group was discontinued. Its brief existence reflected the transitional character of American air organization during the first weeks of the Pacific War, when provisional formations were created quickly, aircraft were redirected between theaters, and units were dissolved once their personnel and equipment could be placed into more permanent combat organizations.
- 1942
B-17s reach Australia
[1]The remaining B-17s traveled via Pacific island bases to Townsville, Queensland, where they became replacements for the 19th Bombardment Group.
- 1942
Organization discontinued
[1]The provisional group was discontinued in early February after its components had been redirected or absorbed elsewhere.
- 1941
Provisional group established
[1]The Army Air Corps created the Sierra Bombardment Group at Minter Field, California, on 8 December, immediately after the Pearl Harbor attack.
- 1941
B-17s depart for Hawaii
[1]The group's B-17 element left for Hawaii on 17 December after a short period of coastal patrol activity from California.
- 1941
B-25 patrols continue from Oregon
[1]The B-25 component remained in Oregon and conducted visual antisubmarine patrols along the Pacific Northwest coast.
Products and positioning
A provisional wartime Army Air Corps formation created for emergency bomber deployment, reconnaissance, and coastal defense during the opening phase of the Pacific War.
Heavy bomber
B-17E Flying Fortress
Ten B-17E Flying Fortresses and associated crews formed the group's heavy-bomber component. They were initially connected with the 7th Bombardment Group and were redirected through Hawaii and the Southwest Pacific before being assigned to the 19th Bombardment Group as replacements.
Medium bomber
B-25 Mitchell
Thirty-five B-25 Mitchells from the 17th Bombardment Group supplied the group's medium-bomber component. These aircraft remained in Oregon and were used for coastal antisubmarine patrols along the Northwest Pacific Coast during the opening period of the war.
Marketing campaigns
- 1941West Coast coastal patrols
California · Pacific Northwest
The group conducted defensive coastal patrols from Muroc Army Airfield and later supported visual antisubmarine patrol activity from Oregon using B-25 Mitchells.
Outcome. The patrols provided emergency wartime surveillance, but the unit lacked specialized detection equipment and recorded no confirmed Japanese submarine sinking off the West Coast.
- 1941Pacific reinforcement movement
Hawaii · Java · Australia
The B-17 component was moved westward after the Philippines crisis, with aircraft passing through Hawaii; some were diverted to Java and others continued across Pacific island stops to Australia.
Outcome. The aircraft were separated from the provisional group and incorporated into the 19th Bombardment Group or its evacuated components.
Recent events
- 1942
Sierra Bombardment Group discontinued[1]
Other
The provisional organization was discontinued in early February after its aircraft and personnel had been transferred or absorbed into other operational formations.
- 1941
Sierra Bombardment Group formed at Minter Field[1]
Other
The United States Army Air Corps established the provisional Sierra Bombardment Group on 8 December 1941, combining B-17 and B-25 aircraft and aircrews for emergency wartime duties.
- 1941
B-17 element redirected through Hawaii and the Southwest Pacific[1]
Other
After beginning coastal patrol activity in California, the group's B-17s were redirected toward the Pacific. Some aircraft went to Java, while the remainder continued through the Pacific to Australia and later joined the 19th Bombardment Group.
- 1941
B-25 component conducted Northwest Coast antisubmarine patrols[1]
Other
The group's B-25 Mitchells remained in Oregon and flew visual coastal antisubmarine patrols along the Pacific Northwest, although the aircraft lacked radar and no Japanese submarine was confirmed sunk off the West Coast.
Sources1 sources
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