World War II: Soviet planes <a href="https://en.wikipedia.org/wiki/Bombing_of_Kassa" id="mwyg" rel="mw:WikiLink" title="Bombing of Kassa">bomb Kassa, Hungary</a> (now <a href="https://en.wikipedia.org/wiki/Košice" id="mwyw" rel="mw:WikiLink" title="Košice">Košice</a>, <a href="https://en.wikipedia.org/wiki/Slovakia" id="mwzA" rel="mw:WikiLink" title="Slovakia">Slovakia</a>), giving Hungary the impetus to declare war the next day.