The Battle of Palo Alto was the first major battle of the Mexican–American War and was fought on May 8, 1846, on disputed ground five miles (8 km) from the modern-day city of Brownsville, Texas. A force of some 3,700 Mexican troops – most of the Army of The North – led by General Mariano Arista engaged a force of approximately 2,300 United States troops – the "Army of Occupation" led by General Zachary Taylor.