It is only WWI.
It is the United States official WWI monument. It was dedicated in 1921. In attendance were Lieutenant General Baron Jacques of Belgium; General Armando Diaz of Italy; Marshal Ferdinand Foch of France; General John J. Pershing of the United States; and Admiral Lord Earl Beatty of Great Britain. They finished bulding in 1923.
The museum closed in the 80s, I think, then opened again in a truncated form. They have remodled it, and it will open again in November.