Liberia joined the Allies in both World War I and World War II. The only troops dispatched overseas were a few individuals to France during World War I, and Liberian volunteers under the command of the United States during World War II. During World War II, U.S. involvement in the country increased greatly. To guarantee a steady supply of rubber from the world's largest rubber plantation, operated at Harbel by the Firestone Company since 1926, the US government built roads throughout the country, created an international airport (known as Robertsfield), and transformed the capital by building a deep water port (the Freeport of Monrovia). During the war, funding provided by the United States allowed an increase in the Force's strength to around 1,500. The armed forces came to rely almost exclusively on American assistance in terms of training, with non-US training "tendto be brief and uninspired [with little accomplished other than some desultory close-order drill."