Henry's return to the throne lasted less than six months. Warwick soon overreached himself by declaring war on Burgundy, whose ruler responded by giving Edward IV the assistance he needed to win back his throne by force. Edward returned to England in early 1471, after which he was reconciled with Clarence and killed Warwick at the Battle of Barnet. The Yorkists won a final decisive victory at the Battle of Tewkesbury on 4 May 1471, where Henry's son Edward of Westminster was killed.