Throughout its storied history, the relationship between Belgium and Germany has been a complex and intriguing one, marked by both periods of unity and division.

While Belgium has never formally been a part of Germany, the two nations have shared deep cultural, political, and economic ties that have shaped the course of European history.

At various points in the past, the lands that now make up modern-day Belgium have fallen under the influence or direct control of German powers.

During the Middle Ages, much of what is now Belgium was part of the Holy Roman Empire, a vast political entity dominated by German nobility. - https://germanyfocusguide.com/blog/did-belgium-ever-belong-to-germany/?unique_id_ww2h3166

"The Intertwined Histories of Belgium and Germany: A Geopolitical Examination"