When King Gustavus Adolphus of Sweden landed in Germany Bernard quickly joined him, and for a short time he was colonel of the Swedish life horse guard. After the Battle of Breitenfeld (1631), he accompanied Gustavus in his march to the Rhine and, between this event and the Battle of the Alte Veste, Bernard commanded numerous expeditions in almost every district from the Moselle to Tyrol. At the Alte Veste he displayed great courage, and at the Battle of Lützen (1632), when Gustavus was killed, Bernard assumed the command, killed a colonel who refused to lead his men to the charge, and finally by his furious energy won the victory at sundown.