The Victory was ready to sail by 17 March, after extensive repairs to make good the damage at Trafalgar. This was to be both her first and her last seagoing commission after that battle, apart from brief trips in the winters of 1808/9 and 1810/11 to Corunna and Lisbon as a troopship. The Admiralty lingered over giving Saumarez his final instructions and he hung around London, impatiently waiting. The reasons for the delay in his departure became apparent on 21 April. ‘The causes of my detention in Town on Monday was in consequence of Ministers having decided to send troops to the Baltic under the Command of Sir John Moore and Lord Castlereagh fixed for seeing us on this Day at one o’clock.’ On 21 February 1808, Russia had declared war on Sweden, invading Finland nine days later. This would provide a buffer against an attack on St Petersburg which lay rather exposed at the head of the Gulf of Finland. Czar Alexander also wanted to show some gain from the French alliance to his nobles, who were discontented at the feared loss of trade with Britain that it would bring and contemptuous of Napoleon. He had a low opinion of Sweden's antiquated army and poor generals, and believed that Finland could be captured easily and quickly.

The Swedes retreated westwards and on 6 April Admiral Cronstedt, the Governor of Sveaborg, the major Finnish fortress near where Helsinki now stands, agreed to surrender it if he was not relieved by five ships of the line by 3 May. Since the ice did not clear till after that date there was no way this would have been possible. It is quite probable that the fortress would have fallen anyway and Cronstedt, as an experienced commander, may have seen this and have taken what seemed to be the best way out in terms of avoiding pointless loss of life. However, Carl Nordling makes a strong case supporting the popular belief, reported by Saumarez to his wife Martha, that it was treachery by Cronstedt, and Hans Hansson has found some references in Russian and French sources that bribery was involved. It is also true that the Swedish people as a whole, especially the nobility, did not support the war.