During the siege of Grave the following year Dudley attempted its relief but the Dutch garrison commander Hadewij van Hemert surrendered the town to the Spanish. Dudley was furious on hearing of Grave's sudden loss and had van Hemert executed, which shocked the Dutch. The English force then had some successestaking Axel in July and Doesburg the following month. Dudley's poor diplomacy with the Dutch however made matters worse. His political base weakened and so too did the military situation. Outside Zutphen an English force was defeated in which notable poet Philip Sidney was mortally wounded, which was a huge blow to English morale. Zutphen itself and Deventer were betrayed by Catholic turncoats William Stanley and Rowland York which further damaged Leicester's reputation. Finally Sluis with a largely English garrison was besieged and taken by the Duke of Parma in June 1587 after the Dutch refused to help in the relief. This resulted in mutual recriminations between Leicester and the States.