The A-20A initially entered service with the USAAF in mid-1941, first being issued to the 3rd Bombardment Group (Light) based at Savannah, Georgia. A-20As were soon issued to the 27th Bombardment Group (Light). The engines of the A-20A were prone to overheating, and to alleviate this problem holes had to be cut around the periphery of the cowling just aft of the cylinder baffles. As soon as engine cooling problems had been corrected, the Army commented favorably on the qualities of the A-20A. The A-20A demonstrated its outstanding features during war games held at Shreveport, Louisiana during September of 1941. It had a performance comparable to that of many first-line fighter aircraft of the period.
The 58th Bombardment Squadron received A-20As in late 1941, and was stationed at Hickham Field in Hawaii at the time of the Japanese attack on December 7, 1941. Two of its aircraft were destroyed on the ground during the attack. At this time the 27th Bombardment Group (minus its A-20As) was in the process of being sent to the Philippines where it was to have been re-established as an A-20 unit. However, no A-20s were available at that time to equip the 27th, and the first operational unit to fly the A-20 in actual battle was the 89th Bombardment Squadron of the 3rd Bombardment Group which began operations from Port Moresby in New Guinea on August 31, 1942.
Shortly after the entry of the United States into the war, the USAAF adopted the British practice of assigning popular names to its aircraft. The USAAF A-20As were assigned the popular name Havoc, since intruder and night fighter versions of the related DB-7 serving with the Royal Air Force had already been so named
In early 1944, the 3rd Bombardment Group was joined in New Guinea by the 312th and 417th Bombardment Groups. The 312th and 417th Bombardment Groups began their combat operations with the A-20G from the start and the 3rd BG converted to the A-20G at about the same time. In September of 1944, there were 370 Havocs on duty with the Fifth Air Force in the South West Pacific Area. They received quite a bit of action in the New Guinea theatre of operation. Most sorties were flown at low level, since Japanese flak was not nearly as intense as was German flak in Europe. During these low level bombing operations, it was found that there was little need for a bomb aimer. Consequently, the bomb aimer was often replaced by additional forward-firing machine guns mounted in a faired-over nose. The A-20's heavy firepower, maneuverability, speed and bombload made it an ideal weapon for pinpoint strikes against aircraft, hangers, and supply dumps. In formation, their heavy forward firepower could overwhelm shipboard anti-aircraft defenses and at low level the A-20s could skip their bombs into the sides of transports and destroyers with deadly effect. These tactics were initially worked out by Army Captain Paul I. "Pappy" Gunn, who also adapted the same tactics to the B-25 Mitchell. The spectacularly successful results of these field adaptations led to increases in the forward firepower of production A-20 which were introduced on the production line with the A-20G model.
Some Fifth Air Force A-20s had their heavy forward-firing armament supplemented by clusters of three Bazooka-type rocket tubes underneath each wing. These tubes each held an M8, T-30 4.5-inch spin-stabilized rocket. These rocket launcher tubes turned out to be heavy and complicated, and were generally more trouble than they were worth and were not often used.
The A-20 groups turned their attention to the Philippines following the end of the New Guinea campaign. By mid-April of 1944, three full four-squadron A-20 groups of the 5th Air Force were active in the island hopping campaign that led to the invasion of Luzon on January 7, 1945. After the Philippines were secured, A-20 units turned their attention to Japanese targets on Formosa in early 1945.
The 312th Bombardment Group had been originally scheduled to replace its A-20s with A-26 Invaders in early 1945, but General Kenney rejected the A-26, maintaining that it did not meet the needs of strafer units in the Southwest Pacific arena and a decision was made for the group to convert to the B-32 Dominator and become a Heavy Bombardment Group. Both the 386th and the 387th Squadron had completed the change by the end of the war, but the 387th and 389th Squadrons still had their A-20s. The 417th BG did transition to the A-26, however.
The old 3rd Bombardment Group still retained its A-20s until the end of the war, becoming the last operational Army A-20 unit. At the end of the war, it was in preparation to move to Okinawa in anticipation of the invasion of Japan.
Although the Boston/Havoc had been in RAF service for some time, it took a long time before USAAF A-20 crews could become operational in the European theatre. In Europe, USAAF A-20 crews actually flew their first combat missions while attached to RAF units. A single USAAF crew from the 15th Bombardment Squadron flew a Boston III from No. 226 Squadron RAF on a sortie on June 29, 1942. Six crews from the 15th flew Boston IIIs from No 226 Squadron to join RAF crews in a July 4 raid against the Hazebrouck marshaling yards in Belgium. This raid was publicized (incorrectly) as the first American air attack on German forces. Three Havocs were lost and three damaged in what was essentially a public relations operation to make up for previous American inactivity in Europe. The 15th Bombardment Squadron later acquired its own Boston IIIs from RAF stocks, but was transferred in November 1942 to Algeria, where it was largely used for training duties.
The first sizable commitment of A-20s under American control did not take place until after Operation Torch, the Allied invasion of North Africa in November of 1942. The first USAAF A-20 group to participate in large-scale combat in the North African theatre was the 47th Bombardment Group. The crews used ferry tanks on their A-20s to cross the Atlantic. The 47th BG flew its first combat mission from Youks-les-Bains, Algeria on December 13, 1942. A-20s provided valuable tactical support to US and British ground forces, especially during and after the Kasserine Pass defeat. Their support helped save the day, and eventually the Germans were forced back into a small perimeter in Tunisia.
During the North African campaign, many of the A-20Bs were fitted with additional forward-firing machine guns in the faired-over bomb aimer's position. Following the German surrender in Tunisia in May of 1943, the 47th subsequently moved to Malta, Sicily, Italy, Corsica, France, and then back to Italy where in January 1945 it began to exchange its A-20s for A-26 Invaders.
While the campaign in North Africa was still underway, plans were made to build up a tactical air force in support of the upcoming invasion of Europe. Three A-20 Bombardment Groups, the 409th, 410th, and 416th were assigned to the 9th Air Force. The A-20G-equipped 416th Bombardment Group began operations in March of 1944 as part of the 97th Combat Bombardment Wing (Light) of the Ninth Air Force. In April and May of 1944, the similarly-equipped 409th and 410th Bombardment Groups joined the 416th. Due to heavy German ground fire, losses during low-level attacks against fixed targets were prohibitively high and had to be stopped. They were replaced by medium-altitude raids led by specially- modified A-20Gs equipped with Boston III glazed noses, which were later replaced by glass-nosed A-20Ks. The A-20G-equipped groups followd the advancing Allied forces into France, but by the end of 1944 the 409th and 416th BGs had converted to A-26 Invaders. The 410th began flying night missions during the winter of 1944-45, but by the time of V-E Day this unit had also been re-equipped with Invaders.
Following the end of the war, the Havocs and appropriated Bostons had
become surplus to USAAF requirements, and most were immediately
scrapped. However, a few surplus Havocs were offered on the surplus
market at very attractive prices--only $3000 apiece with a full tank
of fuel. Nevertheless, the A-20 never became very popular on the
civilian market. Converted A-20s were given a Limited Type
Certificate which did not allow them to carry passengers for revenue.
A couple of surplus Havocs were converted to high-speed executive
transports in which their interiors were modified with luxurious
accommodations, and some were converted as spraying aircraft for
fire-fighting or agricultural work. Less than half a dozen of these
conversions were made.