After the initial skirmishes, Taylor and much of his army marched away from the river to secure the supply line, leaving a makeshift base, Fort Texas. On the way back to the Rio Grande, Mexican forces under General Mariano Arista attempted to block Taylor's way as other troops laid siege to Fort Texas, forcing the U.S. Army general to the attack if he hoped to relieve the fort. In the Battle of Palo Alto, the first major engagement of the war, Taylor's troops forced Arista's from the field, suffering only four dead to hundreds for the Mexicans. The next day, Taylor led the army to victory in the Battle of Resaca de la Palma, putting the Mexican Army to rout. The early successes boosted support for the war, which despite the lopsided votes in Congress had deeply divided the nation. Many Northern Whigs opposed the war, as did others; they felt Polk had used patriotism to manipulate the nation into fighting a war the goal of which was to give slavery room to expand.