Battle of Marcelae in 756 AD
... that three years after the Battle of Marcelae in 756 AD, Constantine V invaded Bulgaria once more but suffered a crushing defeat in the Battle of the Rishki Pass?
...  that three years after the <b id="mwGfg"><a class="mw-redirect" href="./Battle_of_Marcelae_(756)" id="mwGfk" rel="mw:WikiLink" title="Battle of Marcelae (756)">Battle of Marcelae in 756<span id="mwGfo" typeof="mw:Entity"> </span>AD</a></b>, <a href="./Constantine_V" id="mwGfs" rel="mw:WikiLink" title="Constantine V">Constantine V</a> invaded <a href="./Bulgaria" id="mwGfw" rel="mw:WikiLink" title="Bulgaria">Bulgaria</a> once more but suffered a crushing defeat in the <a href="./Battle_of_the_Rishki_Pass" id="mwGf0" rel="mw:WikiLink" title="Battle of the Rishki Pass">Battle of the Rishki Pass</a>?