World War II: The United States declares war on <a href="https://en.wikipedia.org/wiki/Kingdom_of_Bulgaria" id="mwzQ" rel="mw:WikiLink" title="Kingdom of Bulgaria">Bulgaria</a>, <a href="https://en.wikipedia.org/wiki/Kingdom_of_Hungary" id="mwzg" rel="mw:WikiLink" title="Kingdom of Hungary">Hungary</a>, and <a href="https://en.wikipedia.org/wiki/Kingdom_of_Romania" id="mwzw" rel="mw:WikiLink" title="Kingdom of Romania">Romania</a>.