Excubitors
... that three Byzantine emperors in the 6th century served as commanders of the imperial guard, known as the Excubitors, prior to assuming the throne?
... that three <a class="mw-redirect" href="./Byzantine_emperors" id="mwFEU" rel="mw:WikiLink" title="Byzantine emperors">Byzantine emperors</a> in the 6th century served as commanders of the imperial guard, known as the <b id="mwFEY"><a href="./Excubitors" id="mwFEc" rel="mw:WikiLink" title="Excubitors">Excubitors</a></b>, prior to assuming the throne?