The commander of the fortress, Colonel Henrich Danckwardt, was later sentenced to death by a Swedish court-martial for abandoning the fort while it was still deemed defensible.

Maintenance of the fortresses was handled poorly and in early 1719, local fortification experts complained over not getting paid for a long time.

In early June, the blockading naval force increased to seven ships of the line, two frigates, four barges, two floating batteries, one bombarderskip, five galleys and two Galliots.

[6] The strong Danish blockade outside Gothenburg, with an estimated force of 1,300 soldiers and several special-purpose vessels for bombarding coastal defense positions, implied that the Danes were to attack either Marstrand or Älvsborg fortress.

Captain Erik Sjöblad of the Gothenburg Squadron was ordered to moor all frigates and galleys to defend the harbor inlets.

[7] The peace talks in Stockholm failed, and King Frederick IV of Denmark ordered his troops to attack Sweden.

After Rehnskiöld and the commander of the Gothenburg Squadron, Admiral Jonas Fredrik Örnfelt, had assessed the situation and had received intelligence that Norwegian forces were indeed marching towards Strömstad, the order was given to scuttle the transport fleet.

The Gothenburg squadron's galleys Kristiania, Lovisa and Bellona, along with the brig Pollux, were all sunk at Tånge Bay and Tångeflo south of Strömstad on July 5.

Afterwards, Swedish troops under the command of Rehnskiöld totalling around 5,000 – including the garrisons at the fortifications of Gothenburg, Nya Älvsborg and Carlsten – started south towards Uddevalla.

[11] By the end of June, heavy Danish surveillance of the Gothenburg archipelago had been arranged; a force consisting of eight vessels had been deployed between Klåver island and Tjuvkil.

Colonel Henrich Danckwardt, commander of Carlsten had on June 27 requested an additional 400–500 men, to prevent an invasion of Koön and Klåverön (south of Marstrand) but the soldiers had not arrived in time to repel Tordenskjold's attack.

Squadron chief Sjöblad decided that the Hedvigsholm battery should be destroyed, to prevent the cannon falling into enemy hands.

Upon being asked why he had not ordered additional manpower to Hedvigsholm, which was considered the strongest and most effective battery to defend the town, which was also being supported by the galley Prins Fredrik av Hessen, Danckwardt defended his actions by arguing that if he had not destroyed Hedvigsholm, the outwork would have been captured, regardless of its number of personnel.

Ployart demanded access to the fortress but was told that he should speak with the commander, "His excellency" Field Marshal Rehnskiöld, if he wanted anything.

[18] The Danish officer lamented the fact that he could not meet the commander in person and added that if there were any women present in the fortress, they would immediately be given the chance to leave.

[citation needed] After Ployart had returned with the Swedes' rejection, Tordenskjold mounted an assault on the vessels and outworks which were defending the northern harbor inlet.

The Northern Blockhouse suffered the same fate and so the Danes, commanded by Captains Kaas and Kleve, could rapidly enter the city.

In the harbor, the Swedish frigate Kalmar and the galley Greve Mörner continued to defend the northern inlet until the Danish troops eventually entered the city.

Tordenskjolds soldiers managed to prevent the sinking of the frigates Varberg (40 cannons) and William Galley (14), the galiot Prins Fredrik av Hessen (9) and the barge Ge På (18).

At the hearing, Danckwardt was asked why the retreating outwork crews failed to burn the city down, to which he replied that he was not aware that this could have been done any other way except by firing from the fortress.

[25] The Danes transported the captured vessels away from the area, moving up additional mortars and repairing a cannon battery on Koön, which had sustained fire from the Prins Fredrik av Hessen.

All Swedish forces were instructed to leave the fortress by 3:00 p.m., all officers who wished to return to Marstrand were allowed to do so, without being treated as a prisoner of war.

The only breach of the peace was when soldiers from the Saxon regiment and a group of artillerymen broke into a storage facility and stole the butter supply.

[36] Field Marshal Rehnskiöld and his officers were now left with a tough decision: should they stay with the Swedish troops at Uddevalla and protect the roads to Vänersborg and Dalsland or move south towards Hisingen, to avoid being cut off by the Danish forces which could land north of Gothenburg?

Rehnskiöld chose to stay, which turned out to be a good decision since the Danish army at Strömstad later pulled back into Norway at the end of August.

The executioner, Jonas Wessman, was allegedly late and under the influence of alcohol which resulted in him not performing the beheading correctly and was forced to strike three times in order to completely remove the head from the body.

[44] Captain von Utfalls visit to Tordenskjold at Marstrand on July 14, was described in a more detailed way by Danish author Casper Peter Rothe.

[47][48] Rothe's version of the events at Marstrand, describes Danish soldiers humiliating the captured Swedish officers by verbally abusing them and forcing them to dress up in women's decorative clothing.

The regiment, commanded by Colonel Georg David Zengerlein, was composed of Saxon prisoners of war who had been captured during the battles in Saxony-Poland.

Colonel Zengerlein of the Saxon Infantry Regiment was the chairman of the war hearing and he would never have been elected to the position if the Swedes had doubted him or his unit.