While serving in the regiment he participated in the Count of Tilly's campaigns in Bohemia and the Rhine, then took part in the Siege of Magdeburg and at the Battle of Leipzig.

[1] After Baron Geleen distinguished himself in 1632 by the defence of Wolfenbüttel against the Duke of Lüneburg, he received an independent command in Westphalia in June 1633.

With luck and skill, he led his 10,000 Catholic League troops against the desultorily appearing armies of the Landgrave of Hesse-Kassel and the Duke of Lüneburg as well as against the Swedes under Torsten Stalhandske.

[1] In early 1641, he helped to drive Banér from the Upper Palatinate and then marched to the Rhine in April, where he spent the next year in Cologne under Hatzfeld on an indecisive campaign against Guébriant.

Soon after leaving the army, Geleen was retired as Province Commander (Landcomthur) of the Teutonic Order in the Bailiwick of Alden Biesen.