A dependence on others.
While Germany holds the UK at bay over Brexit, they should remember that for the last century the country is indebted to the USA and the UK for its economic survival.
After World War 1, Germany was in tatters, and without the US Lend Lease project they would never have recovered; despite the conditions of the Treaty of Versailles banning them for building warships, they disregarded this proviso and built an Imperial Navy.
After the end of World War 2, it was again American money in the guise of the Marshall Plan that stopped the Russians from taking over Germany. The many critics of US Foreign Police forget that they saved many countries from becoming Communist, and lost thousands of young men in doing it when if they'd followed the policy of Woodrow Wilson they could have stayed out of the conflicts.
Now they hold the UK at knifepoint over Brexit, even though without the money from the UK, Germany would be in such an economic mess after decades of bad decisions that the country would not recover.