During the Battle of Resaca de la Palma on May 9, 1846, the two sides engaged in fierce hand-to-hand combat. The U.S. Cavalry managed to capture the Mexican artillery, causing the Mexican side to retreat—a retreat that turned into a rout. Fighting on unfamiliar terrain, his troops fleeing in retreat, Arista found it impossible to rally his forces. Mexican casualties were significant, and the Mexicans were forced to abandon their artillery and baggage. Fort Brown inflicted additional casualties as the withdrawing troops passed by the fort, and additional Mexican soldiers drowned trying to swim across the Rio Grande. Taylor crossed the Rio Grande and began his series of battles in Mexican territory.