Following his mission as Minister Plenipotentiary Erdmann joined the international staff of NATO Headquarters, Brussels in summer 2005.
In January 2010 he returned for a short period to the Foreign Office in Berlin until he was appointed Permanent Representative of the Federal Republic of Germany on the North Atlantic Council, Brussels in March 2010.
From 1 October 2014 until end of July 2015 he acted as Dean of the North Atlantic Council (NAC).
During his time in office, Turkey's Foreign Ministry summoned him in March 2016 over a satirical broadcast by German television station NDR that featured "Erdowie, Erdowo, Erdoğan", a two-minute satirical song mocking Turkish President Recep Tayyip Erdoğan.
[1] In March 2017, the foreign ministry summoned him again after the municipality of Gaggenau in southwestern Germany revoked permission for a campaign event for that year's constitutional referendum at which Turkish Justice Minister Bekir Bozdağ was to appear.