agreed to implement
... that on 9 January 1917, German Emperor Wilhelm II agreed to implement unrestricted submarine warfare?
... that on 9 January 1917, German Emperor Wilhelm<span id="mwBn0" typeof="mw:Entity"> </span>II <b id="mwBn4"><a href="./9_January_1917_German_Crown_Council_meeting" id="mwBn8" rel="mw:WikiLink" title="9 January 1917 German Crown Council meeting">agreed to implement</a></b> unrestricted submarine warfare?