service of marriage
... that instead of fighting in battle, female vassals in the Kingdom of Jerusalem were obliged to render the service of marriage to their lord by marrying one of three candidates proposed to them?
... that instead of fighting in battle, female <a href="./Vassal" id="mwB2w" rel="mw:WikiLink" title="Vassal">vassals</a> in the <a href="./Kingdom_of_Jerusalem" id="mwB20" rel="mw:WikiLink" title="Kingdom of Jerusalem">Kingdom of Jerusalem</a> were obliged to render the <b id="mwB24"><a href="./Service_of_marriage" id="mwB28" rel="mw:WikiLink" title="Service of marriage">service of marriage</a></b> to their lord by marrying one of three candidates proposed to them?