 Complete the following phrase:  The poncho was first used on a regular basis in the 1850s for irregular U.S. military forces operating on the U.S. Western Plains. These early military ponchos were made of gutta percha muslin, a latex-coated, waterproof cloth. Ponchos made of gutta-percha or India rubber coated cloth were officially adopted during the American Civil War, both as rain clothing and as a ground sheet for sleeping. While originally intended for cavalry forces, they were widely used by infantry as well; General Shermans Union troops, lightly equipped and living off procurement demand from the local populace, wore ponchos during wet weather encountered during the 