a war alliance. The Polish–Lithuanian union also joined, desiring control of the Baltic trade. Skirmishes broke out in May 1563, before war was officially declared in August that year. War Initial phase In May, the first movements of the war started as a Danish fleet under Jakob Brockenhuus sailed towards the Baltic. At Bornholm, on 30 May 1563, the fleet fired on the Swedish navy under Jakob Bagge, even though war had not officially been declared. A battle arose that ended with Danish defeat. German royal emissaries were sent to negotiate a peace, but at the meeting place of Rostock no Swedes appeared. On 13 August 1563, war was declared by emissaries from Denmark and Lübeck in Stockholm. The same month, Danish king Frederik II attacked Älvsborg. At the beginning of the war the Danes advanced from Halland with a 25,000-strong army of professional mercenaries and captured Sweden's gateway to the west, Älvsborg Fortress, after only three days of bombardment and a six-hour assault on 4 September. This achieved the Danish aim of cutting off Sweden from the North Sea, blocking the all-important salt imports. Eric then attacked Halmstad, without result; the Swedish counterattack was driven back by the professional Danish army. After the king's departure from his army, Charley de Mornays stepped in as the commanding officer and was beaten by the Danish at the Battle of Mared. At sea a battle broke out near Öland on 11 September, whereafter the war took a pause. Campaigns South On 30 May 1564 a battle broke out between the Swedish navy and the Danish–Lübeck navy between Gotland and Öland. The Swedish navy was under the command of Jakob Bagge, and the Danish–Lübeck navy was under the command of Herluf Trolle. Bagge was captured and the largest warship of the Baltic, the Mars (also known as the Makalös), sunk. The Swedish navy retreated to Stockholm leaving a sea blockade in effect. Klas Horn became the new commander and met the Danish fleet at the island Jungfrun north of Öland 14 August. An inconclusive fight left the sea blockade in effect. Horn attacked the provinces Halland and Skåne in 1565 and made several attempts at Bohuslän and Uddevalla. The Danish burned old Lödöse in the province of Västergötland. Eric initially led the army against the Danish himself, but then turned over command to Nils Boije, who on 28 August 1564 took Varberg. The