Beker was an adjutant general on the staff of Jean-Mathieu-Philibert Sérurier at the Battle of Magnano in 1799. Soon after Marengo, Beker married the deceased Desaix's older sister Antoinette Desaix (1764–1816). He was elevated to the rank of general of brigade on 2 January 1801. He fought with the Army of Santo Domingo in 1802.