The answer is very simple. Germany has become the vassal state of Turkey
A million Turkish live in Germany, and the Turkish dictator keeps a large part of them under his control. They have to serve the Turkish army for example.
You are under-estimating the number of Turks in Germany. According to the official stats, the real number is close to 4 million, out of which 1,506,113 holds the Turkish citizenship. In 1998, 2.11 million German residents had Turkish citizenship, but the numbers have fallen as many have opted for the German citizenship. And obviously, if you are a Turkish citizen, then you have to serve in the Turkish army.