By 1632 he was in Austrian service in Bohemia, commanding an infantry regiment. De Haes fought in the Battle of Lutzen (1632), the Siege of Ingolstadt, and the Battle of Nördlingen (1634). In 1635 he was appointed general of the Army of Tyrol, occupying the Valtelline in 1637. He was injured in the Battle of Ziegenhain (1640), and spent six months recovering.