Enraged Walker ordered the invasion of Costa Rica and a filibuster force crossed the border into Guanacaste, while the Costa Rican army moved down from the Central Valley in the same direction. With the army traveled the President but command was in the hands of his brother, Jose Joaquin Mora, and his brother-in-law, General Cañas. Upon hearing that a small contingent of men were encamped near the city of Guanacaste's Hacienda Santa Rosa Mora led three thousand of his men to attack. Walker's men were under the command of Colonel Louis Schlessinger, an inexperienced officer. On the 20 March with no sentries posted, Mora's Costa Ricans surprised and attacked the small group; Schlessinger himself ran away, leaving his troops vulnerable, disorganised, and without leadership.