The proportion of three-wheeled trucks that contributed to Japan's recovery after the war peaked at 72 percent of overall truck production in 1953. From that point on, small four-wheeled trucks began to take over. At the time, Japan's economy was enjoying a period of rapid growth and demand was quickly rising for comfortable four-wheeled trucks. Mazda, which had been producing small four-wheeled trucks in low volumes since 1950, did not let this opportunity pass by, and in April 1958 brought out the new Romper cab-over semi four-wheeler. This model had a robust body, superbly nimble performance and plenty of other attributes. It also shared all the latest technology that had been cultivated in the development of Mazda's three-wheeled trucks. The Romper had a 32.5ps water-cooled, twin cylinder engine and a one-ton load capacity. In March the following year (1959), Mazda introduced the D1100, equipped with an advanced water-cooled four-cylinder DHV engine delivering outstanding power (1-ton class, 46ps) as well as the D1500 (1.75-ton class, 60ps). The 1-ton 46ps model was the most powerful in its class and quickly earned a strong reputation, boosting Mazda's share of the small truck market from four percent in 1958 to more than double (ten percent) in 1959.