Answer:
He later served as the army's Commanding officer in Berlin, Germany, where his headquarters had formerly been occupied by the very Nazi leaders who had put his family in the camp and killed many of his family members.
Step-by-step explanation:
Irony is when what happened is not something that is expected. This means that the expected outcome of anything is so far from what actually happened, surprising the people.
Here, the word "delicious" is added to modify the 'irony'. By adding the word "delicious", the speaker seems to suggest the fact that the irony is something that both surprises yet makes him happy or even excited about it. And the "delicious irony" in the passage is "his headquarters (in Berlin, Germany) had formerly been occupied by the very Nazi leaders who had put his family in the camp and killed many of his family members." This ironic outcome seems to be both cathartic and painful for him.