The Douglas B-18 Bolo was America's most numerous bomber when war arrived in 1941.

Wars & Conflicts · Published 15 October 2026 Swipe more like this →

In short: Designed during the Great Depression as a budget-friendly alternative to the Boeing B-17, the Douglas B-18 Bolo was already obsolete by the time it entered service. Despite its limited range and speed, this twin-engine bomber became the backbone of American air power before being relegated to anti-submarine patrols.

In 1934, the United States Army Air Corps sought a new twin-engine bomber to replace the Martin B-10. Douglas Aircraft Company entered its DB-1 design, competing against the Martin 146 and the Boeing Model 299. While the Boeing design was technically superior, its four-engine configuration disqualified it from the competition. Furthermore, the DB-1 was significantly cheaper, costing $58,500 compared to $99,620 for the Boeing entry. This price advantage, coupled with the economic constraints of the Great Depression, led to the B-18 being ordered into production in January 1936.

The B-18 was essentially a modified DC-2, featuring a deeper fuselage and a mid-wing position to accommodate an internal bomb bay. However, its performance quickly fell behind international standards. By 1939, foreign aircraft like the Soviet Ilyushin TsKB-30 and the Japanese Mitsubishi G3M2 demonstrated vastly superior range, speed, and defensive capabilities. The Air Corps eventually conceded that the Bolo was unsuitable for its intended combat role. Nevertheless, it remained the most common American bomber deployed outside the continental United States when the attack on Pearl Harbor occurred in December 1941.

Following the destruction of many overseas Bolos in the initial Pacific onslaught, the remaining aircraft were repurposed. In 1942, 122 B-18As were converted into B-18B anti-submarine variants, equipped with search radar and magnetic anomaly detection gear. These aircraft served in the Caribbean and with the Royal Canadian Air Force, where they were known as the Digby. While they successfully sank German U-boats, including U-654 and U-520, they were soon superseded by the more capable B-24 Liberator. By the end of the war, the surviving Bolos were relegated to training or transport duties, eventually being sold as commercial surplus.

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