 He held this position through December 2001, when he was promoted brigadier general and given the Chief of Staff position of the First Combined German-Dutch Army Corps in Münster.As Chief of Staff of this corps he oversaw the transformation of the corps' headquarters to a "High Readiness Force (HRF)" headquarters.During his tenure as Chief of Staff the First Combined Corps' Headquarters was assigned command of the ISAF mission in Afghanistan, which led to a seven-month tour for Bertholee in Kabul as Deputy Commander and Chief of Staff for ISAF III.