 The attacking force consisted of approximately 6,600 American soldiers, most of them regulars, armed with the then-new smokeless-powder Krag–Jørgensen rifle and supported by artillery and Gatling gun fire.Though the assault was successful, the Americans soon realized that they had suffered more than 1,400 casualties in the assault.A U.S board of investigation pinned the blame on the superior firepower of the Spanish Model 1893 Mauser rifles, although modern analysis has determined that many of the casualties were due to superior Spanish fortifications on the high ground.