<a href="https://en.wikipedia.org/wiki/World_War_I" id="mwAS0" rel="mw:WikiLink" title="World War I">World War I</a>: The <a href="https://en.wikipedia.org/wiki/1st_Army_(Russian_Empire)" id="mwAS4" rel="mw:WikiLink" title="1st Army (Russian Empire)">First Russian Army</a>, led by <a href="https://en.wikipedia.org/wiki/Paul_von_Rennenkampf" id="mwAS8" rel="mw:WikiLink" title="Paul von Rennenkampf">Paul von Rennenkampf</a>, enters <a href="https://en.wikipedia.org/wiki/East_Prussia" id="mwATA" rel="mw:WikiLink" title="East Prussia">East Prussia</a>.