[2] However, the Danes stalled and prolonged the fulfillment of some provisions of the earlier peace; the Swedish king decided to use this as a pretext to attack with an ambitious goal: to vanquish Denmark as a sovereign state and raze the capital of Copenhagen.

This failed when the Dutch Republic joined the conflict on the Danish side and a reinforcing fleet managed to smash its way through the Swedish naval forces in Øresund.

Denmark-Norway had been forced into a humiliating peace in the Treaty of Roskilde in which Denmark had to cede Scania, Halland and Blekinge on the Scandinavian Peninsula and the island of Bornholm, and Norway lost the provinces of Båhuslen and Trøndelag.

The Swedish king knew that the army would not be able to be supplied in Sweden for long, and disbanding it was not desirable with the Poles eager to revenge the 1655 invasion of Poland-Lithuania.

[3] When the Danish stalled and prolonged the fulfillment of some provisions of the earlier peace treaty the Swedish king decided to use this as a pretext to attack with a breathtaking goal: to vanquish Denmark as a sovereign state, raze the capital of Copenhagen and divide the country into four administrative regions.

However, even this ambitious goal was just to be stepping stone towards the ultimate plan of a quick conquest of Denmark so that the Swedes could wage a campaign in Europe without risking Danish interference.

The city also had plenty of defensive materiel: 50 tonnes (110,000 lb) of lead, 4,000 muskets, and a staggering 810 kilometres (500 mi) of slow match.

On August 23, 1658 almost 3,000 students, sailors and soldiers staged a surprise sortie through a hidden passage in the wall,[10] destroying fortifications under construction and capturing three cannons.

[11] Over 200 heated shot a day were hurled into the city, and several large howitzers were brought to bombard the Danish capital, including the 300-pounder "Eric Hansson", earlier used in the siege of Kraków.

The Lord High Admiral of Sweden, Carl Gustaf Wrangel, resorted to subterfuge and spread the rumor that Copenhagen had fallen and the Swedish soldiers started a false celebration.

The loss of Kronborg was a blow for the Danish; 77 captured cannons were quickly put to use in the siege and with the castle in Swedish hands, it was believed that the Dutch would have a difficult time to come to aid.

Standing against them was a Swedish navy force led by Carl Gustaf Wrangel and Admiral Klas Hansson Bjelkenstjerna, consisting of 43 ships, with 1,605 cannons and 4,055 sailors.

Charles personally fired the first hostile shot from Kronborg, but it fell short; the Dutch had wisely chosen to sail closer to the Swedish side, where there were fewer land-based guns to contend with.

The Swedes got very close to Nyboder and were in the process of crossing the moat, when they fell victim to a well-conducted ambush, and withdrew with heavy losses.

Not only had their arch-enemy been defeated, out of the smoldering city came a stronger bourgeoisie with renewed confidence, more privileges and an improved position vis-a-vis the Danish crown.

[27] Swedish possessions in Central Europe all along the Baltic coast were under attack, and the Austrians at least were enthusiastic in Pomerania sending an army of 17,000 to lay a siege on Stettin where they joined 13,000 Brandenburgers.

[28] Nevertheless, the allies managed to take possession over Jutland and the Swedish commander Philip of Sulzbach was forced into a long series of retreats.

England worked hard to broker a peace, aided by France which also declared its willingness to help the Swedes if the Danes refused to negotiate.

Major general Ernst Albrecht von Eberstein was in charge of the allied forces that had been left on Jutland, and was also moving towards Funen; landfall was made two days later without any Swedish resistance.

[36] The Latvian city of Mitau (Jelgava) fell to Polish-Lithuanian forces commanded by Aleksander Hilary Połubiński in January 1660 and the allies were preparing an invasion of Zeeland; the outlook was not good for the Swedes.

[citation needed] The first Swedish attack on Frederikshald started on 14 September 1658 with a force of 1600 under Harald Stake, who falsely believed the town to be undefended.

But Frederikshald was defended by two companies of the civic militia under captain Peder Olsen Normand, who had taken up a position on the Overberget hill south of the town.

Harald Stake was back with 4000 men, who approached the town across the frozen inlet of Svinesund and opened artillery fire from the island Sauøya.

[citation needed] An even greater Swedish force of 5000 soldiers (of which 3000 were cavalry) under Lars Kagg, Gustaf Horn and Harald Stake laid siege to Frederikshald in January 1660.

[citation needed] Already on September 28, 1658, a small fleet of three ships and several smaller boats landed the Norwegian forces close to Trondheim.

Charles X ordered Lieutenant Colonel Erik Drakenberg to assemble a force in Jämtland and march towards Trondheim, but the relief was stopped by Norwegian peasants that had taken to the hills and defended the mountain passages.

The island was seething with anger and resentment, and after the Swedish invasion of Denmark Frederick III sent letters to leading men in the community, urging them to revolt.

[41] One of Frederick III's bodyguards, Statius, traveled to Scania to organize the peasants into Snapphane units and instigate anti-Swedish sentiment.

[43] With the death of the Swedish king, one of the major obstacles to peace was out of the way; in April the Treaty of Oliva was signed with the Allies (Polish-Lithuanian Commonwealth, Austria and Brandenburg).

[44] The Danish statesman Hannibal Sehested was instructed by Frederick III to negotiate with the Swedes, and the resulting peace treaty can largely be credited to him.