[9] A States and English army under Prince Maurice of Orange and Horace Vere respectively crossed the Scheldt estuary and advanced on land taking Cadzand, Aardenburg, and IJzendijke in the Spanish Netherlands.

[14] This never happened however as disputes in the Dutch command meant that taking Spanish occupied areas in the rest of the Netherlands took priority as the opportunity arose.

[18] The prolific Dutch statesman Johan van Oldenbarnevelt knew that with the death of Elizabeth I the year before, the new king of England James I had been approached by the Spanish for peace proposals.

[19] Afraid that the new peace would sever the Dutch coastal towns in English hands, given in 1585 as part of the Treaty of Nonsuch, Oldenbarnevelt's attention then soon turned to the Cadzand area south of the Western Scheldt.

[22] Being in possession of Sluis would help them to secure the Scheldt, which was on the approach to the important port city of Antwerp and control of the Zwin, which was also the route to Bruges.

[27] Another 1,400 galley slaves (mostly Turks) and a large number of warships including ten war gallies were also in the town, as were hundreds of civilians who were determined to stay.

[28] In total the combined Dutch and English army numbered 11,000 soldiers – Maurice was accompanied by his young brother Frederick Henry who was now second in command after Sir Francis Vere who was convalescing his war wounds as governor of Brielle.

[22] A vast number of vessels had been collected, and the Dutch and English army crossed the Scheldt and on 24 April successfully landed on the opposite shore between Vulpen and Cadzand.

[29] The Dutch and English army then moved forward to the town of IJzendijke a strongly fortified place three leagues to the east of Sluis which consisted of a largely Italian garrison and invested it by 6 May.

[22] Before a close siege could be formed it was however necessary to outmanoeuvre the efforts to relieve the garrison, not only of Don Luis de Velasco, the Spanish general of horse.

[8]: 144  Velasco had entrenched his force of 2,000 men in a narrow pass, in front of Damme, the town between Sluis and Bruges in a position known as the Oostburg Line.

As a result, the Dutch suddenly fell backwards down the stream to a point which Velasco, who had been in pursuit, had discovered it to be fordable at low water.

[27] Fairfax led his men to the attack with great vigour and after a sharp engagement, he forced the Spanish to retire behind their entrenchments, and followed them so closely that they were routed.

[31] The Spanish held fort of St. Joris with a garrison of 300 men, armed with nine guns, was now isolated and soon surrendered which meant that Sluis could be besieged proper.

[32] Colonel Van der Node, who had been governor of Ostend, crossed the Zwin at low water with thirty companies, of which ten were English.

[8]: 146 In July, Spinola himself made another attempt to relieve Sluis under orders from the Archduke saying that Spain could not afford to lose another Flemish port.

[31] Maurice however saw the plan and set a large force to work, and in forty-eight hours he had dug a trench across, which effectually stopped the passage.

[6] He then mounted several guns between the quarters of Van der Node and Count William, and opened a heavy and continuous fire on the camp of Spinola.

[23] By now hunger and infectious diseases took their toll on the civilians and soldiers alike in Sluis, but eventually news of the Spanish relief force was on the way and much hope was somewhat restored.

[10] News of the capture of Sluis was celebrated in England - in London at St Katharine Docks vessels fired salutes in honour of the victory.

[36] On 22 September Daniel de Hartaing then surrendered Ostend as ordered by Maurice and by agreement from the Hague; the city was nothing but a mass of ruins.

[6][8]: 146  South of Sluis a line of fortifications was put in place – access to the Zwin was shut off, town walls were strengthened along with fortresses on both sides of the front.

Due to a clever piece of wording in the Treaty of London however the Dutch could still recruit English and Scottish soldiers but in the pay of the States as volunteers.