He made a name for himself as a siege specialist, taking or successfully defending many fortified cities along the Dutch-German border.

In 1644, he defeated a Duchy of Lorraine force at the Rur (Roer) River near Eschweiler but was intercepted and captured on his way back to the Hessian stronghold Neuss by imperial troops under Christian von Nassau-Siegen.

[1][2] Later in 1644, he occupied Xanten until Hessian regent Amalie Elisabeth handed it back to its ruler Frederick William of Brandenburg through Dutch mediation.

Rabenhaupt recaptured Jemgum from the Imperials and returned to Hesse in the hope of becoming supreme commander of the Hessian forces.

[1] After dedicating many years to science and religion on his estates in the Netherlands, Rabenhaupt was recruited by the Dutch Republic in 1671 as colonel of his own regiment, and later promoted to lieutenant general.

The garrison under Noël Bouton de Chamilly inflicted heavy casualties on the besiegers and only capitulated on 27 October to Rabenhaupt and Stadtholder William of Orange.