What does it mean that the
"world was [his) oyster?”

You're close, but in place of “ability,” I'd say “opportunity,” and rather than “accomplish anything you put your mind to,” I'd go with “profit from your position.”

Explanation:

The Oxford English Dictionary (OED) explains the idiom “the world is one's oyster” as meaning that “one is in a position to profit from the opportunities.

after the signature of the treaty of versailles in june 1919, germany lost nearly 25,000 square miles and a population of 7 million people. these territories included eupen-malmedy area and moresnet which were ceded to belgium. regarding relations with france, germany ceded the sovereignty of the saar coal mines to this country, as well as the provinces of alsace-lorraine.

explanation:

the answer is irony!