Cronstedt was born on Botby mansion (now a part of Helsinki) in Finland 3 October 1756. His parents were Johan Gabriel Cronstedt and Hedvig Juliana Jägerhorn af Spurila. He joined the army in 1765 and advanced to the rank of lieutenant in 1773. Only five years later, he was promoted to the rank of lieutenant colonel. When Sweden in 1788 declared war on Russia he fought in the royal navy. In 1790 he won a great naval victory against the Russian fleet at the naval battle of Svensksund (in the Gulf of Finland). The naval battle is the greatest naval battle in the Baltic Sea history.
After the naval battle he was promoted to the rank of colonel and was appointed to naval state secretary. After further advances he was soon to become vice admiral. However, shortly after he was to be in disfavor of the new king and was appointed to be commander of Sveaborg. Cronstedt had desires to be commander of the whole royal fleet, not commander of some distant fortress in Finland.
In 1801, he was elected a member of the Royal Swedish Academy of Sciences, but was expelled in 1809.
After Finnish War, Cronstedt lived rest of his life in his manor in Herttoniemi, near Helsinki.
Cronstedt surrendered the fortress to the Russian army after a siege of two months. The fortress had internationally received the reputation of being "the Gibraltar of the North", and was by some assumed to be impregnable. In the peace treaty next year (1809), Sweden was forced to give up the territory of Finland (about half of the kingdom). In order to find scapegoats for the loss of Finland the surrendering of Sveaborg became a convenient vehicle, and as Cronstedt was the responsible officer, he was charged with the whole catastrophe.
Today, however, many historians are re-evaluating the action of Cronstedt. His decision to surrender the fortress was a great humanitarian act, in order to prevent the children and women within being killed by the Russians (many of the civilians from Helsinki had fled to the fortress and would likely have been be killed if Cronstedt had not reached agreements with the Russians). Furthermore, the war was doomed to a Swedish defeat already from the beginning. Sweden was not in the shape for war with no money or resources whatsoever. Cronstedt was the man to be blamed in order to save the dignity of King Gustav IV Adolf.
War broke out 21 February 1808 on the initiative of the Russian empire. The timing was unusual, as wars were usually fought in summertime, and the temperature at that time was -30 degrees Celsius (-22 F). Because of the cold winter, the poor condition of the Swedish army and the plan to retreat to the north, the Russian army faced poor resistance in Finland. So, the Finnish territory was overrun and half of the kingdom (Finland) was conquered in a few months. The Swedish main force retreated towards Sweden, leaving Sveaborg and Svartholm to defend themselves. The idea was that the fortresses would hold out and that reinforcements would arrive in the next summer. The fortress Svartholm surrendered already on 18 March. The siege of Sveaborg began in early March. After only three weeks of siege, negotiations between Carl-Olof Cronstedt and the commander of the Russian unit Jan Pieter van Suchtelen were held. The negotiations resulted in a deal, that if no reinforcements had arrived by 3 May, the fortress would unconditionally surrender. Unfortunately for the Swedes, the sea was still frozen in May 1808 and royal fleet could not arrive, therefore Sveaborg surrendered on 3 May.
Although much of the happenings are clear, some details are still held in darkness. One reason is that the sea was frozen and the royal navy could not arrive. Furthermore, the messengers sent to Stockholm were delayed by the Russians and arrived too late. It is also disputed if any troops would have arrived anyway, as Sweden had their troops tied with their southern enemy Denmark and their mighty ally France. Interesting though why Cronstedt did not succeed to buy more time and why any negotiations about surrendering were held in the first place, Sveaborg that was supposed to be the uninvadable "Gibraltar of the north". These questions are more complicated to answer.
Reasons:Sveaborg is a bastion fortress, built on principles applied in Europe. This architectural type was considered as the world's most modern in those days. However, bastion fortresses were normally built in central Europe, where the land is flat. As the Finnish archipelago isn't flat at all (the height changes are huge) Sveaborg didn't fit the location very well. As the architecture of a bastion fortress is relying on a symmetrical defense, Sveaborg had lots of weaknesses. The Gibraltar of the north was therefore not a very justified name.
Although the Russian army was at first much smaller (2000 men, 60 cannons) than the forces at Sveaborg (6000 men, 734 cannons), more reinforcements arrived all the time. By the time of the negotiations, the Russian army was larger than the defending force.
The fortress had earlier received very poor funding. Since its completion in 1791, Sveaborg received no extra financial support from the government (the reason for that is still a mystery, but naturally related to the weak Swedish economic situation). The military equipment was in an unsatisfactory condition. Most of the supplies were of bad quality and the fortress was lacking most supplies.
The cannons too, were old and partially obsolete. This meant that their range was shorter than that of the Russian artillery (which is a problem if cannons are stationed on a fortress). The fortress was unable to return fire on the Russian troops that were bombarding the fortress heavily. Furthermore, the fortress was lacking cannons; having not even half the number of cannons that were supposed to be on the fortress (almost 1600 cannons).
Cronstedt claimed that the fortress was in shortage of gunpowder. This has been disputed by some historians as opinions diverge around what should have been sufficient daily battle usage of gunpowder.
The reason for the limited time of one month is that the negotiations were more or less dictated by the Russians. The Russian army was better supplied and had better artillery. The Russian army gave Sveaborg only one month to get reinforcements.
Sveaborg was facing perhaps the world's most mighty army. Even if the fortress had been well built and well supplied, it is arguable if it could have withstood the war.
There are theories about the surrendering of Sveaborg that have never been confirmed or proven. Still, they continue to have support both amongst professionals and laymen. Despite the fact that the large picture is known, we should still consider the possibility of the following theories:The war came surprisingly, and the civilians at Sveaborg were not evacuated in time. They were mostly families of the officers, 2000 civilians. It is possible that the commander, Cronstedt, wanted to save the lives of the women and children at Sveaborg. In those days fortress invasions were very bloody stories and no-one was usually spared.
Cronstedt was even believed to have been bribed by the Russians. Despite recent research this is still a popular theory today. During the Finnish War, two fortresses were located in south Finland: Sveaborg and Svartholm (located nearer to the Russian border). The commander of Svartholm C.M.Gripenberg surrendered the fortress quite immediately to the Russian army. Shortly after he was employed by the Russian army. This was seen by many as bribery, as he was given a good position in the Russian army (officers changing side was very common during this war). Therefore, Cronstedt was also a target for suspicions of bribery. However, the suspicions of Cronstedts bribery have never been confirmed. It is true that he as well was given a pension (Cronstedt refused to join the Russian army and retired shortly after the war) by the Russian emperor, but the amount of money was normal and not much. There were no reports afterwards of any great wealth of Cronstedt. Further, Cronstedt continued after the war to carry his Swedish medals and wanted to defend his actions in front of a Swedish court himself, but was then finally advised to stay in Finland.
It is believed that the Russian army was using war-psychology skillfully. Many of the officers families were living in Helsinki and the Russian army was using the letter correspondency cunningly to convince the officers at Sveaborg that the Russian army was substantially larger than it was and that the whole kingdom of Sweden had been invaded. Many of the officers were suppressing Cronstedt to surrender. Afterwards Cronstedt was criticised for not reckoning the enemy force properly (the reason is still unknown).
A short story "Under Siege" (published in Omni, October, 1985) by George R.R. Martin takes place during the siege of Sveaborg, as well as in a dire future.
The surrender of Sveaborg in undoubtedly one of the most important events in the history of Finland. Therefore, Carl-Olof Cronstedt is naturally a central character of it. In Sweden, he was recognized as a traitor after the war, condemned to death in the court of Stockholm (later abolished on the initiative of the Russian emperor). He alone was made responsible for the loss of Finland, and therefore ending one era in Swedish history. During the earlier, era of greatness Sweden was in the 17th century recognized as a major power in Europe, and now Sweden had become a shadow of its former self.
Cronstedt was also by many condemned as a traitor in Finland. He was made a symbol of an embarrassing war and a failure to stop the Russian army. This war was for long an embarrassment for Finland until Johan Ludvig Runeberg wrote the national romantic poem collection The Tales of Ensign Stål. In this writing Runeberg paints the picture that the Finns fought bravely in the Finnish War and that everything was the fault of a few officers and the king. This was an encouragement for the Finnish national identity, in part built up on the hatred of Cronstedt.
The old legacy of Carl Olof Cronstedt was that Sweden was forced to give up half of its kingdom, whereas modern historians seem to explain the developments at Sveaborg by primarily smart psychological warfare combined with the widely spread low morale among Swedish officers. Today, Sweden and Finland are separate sovereign nations. It is therefore somewhat contradictory that Cronstedt has been seen as a traitor in Finland, when he is one of the main reasons for Finland being an independent nation.
In 1990's Cronstedt was remembered by naming a newly built street in Helsinki after him. Amiraali Cronstedtin ranta (Admiral Cronstedt's Quay) is located about one kilometre from preserved admiral's manor in Herttoniemi.