In 2008 to 2010, Breuer later served as the Deputy Supreme Allied Commander Transformation Representative in Europe (SACTREPEUR) at the NATO headquarters in Brussels, Belgium.

Breuer also served as Project Manager for the creation of the 2016 White Paper on German Security Policy and the Future of the Bundeswehr.

Breuer later served as Deputy Chief of Staff, Operations/Military Intelligence/Training Directorate in 2016 to 2017 before being named as the commander of the Kommando Territoriale Aufgaben der Bundeswehr from 2018 to 2021.

During his stint, Breuer was tasked to highlight the importance of strengthening the country's operational readiness in times of war, amidst the risks posed by the Russian invasion of Ukraine.

The calls were made based on their analysis and stated that an attack "is possible" as Russia continues to build its military muscle amidst its invasion in Ukraine.