During this era, the Glenn L. Martin Company built a new biplane that was one of the few combat planes of the war period conceived in the United States - a twin-engine fighter bomber designated MB-1. It was powered by two 400 horsepower Liberty engines and could accommodate a crew of three.

Although produced too late to be used in World War I, the MB-1 and its various adaptations created high profits for the Martin Company and established the company's reputation.

In 1919 the Army was looking for a 3-seat gunner airplane to support ground troops and was considering the MB-1. Because of the power and weight of the MB-1, Army top brass decided that the plane should be redesigned as a bomber. Bombers had demonstrated their potential during the last few months of World War I, but the U. S. Army did not yet possess one. However, high costs and technical problems cooled the military's enthusiasm for the MB-1. Correspondingly the local Cleveland group of investors withdrew their support in 1920. Martin then took over ownership of the entire company.