The allies decided to attack the Russians in September 1854: the aim was to capture Sebastopol at the south-western tip of the Crimean peninsula, the main base of Russia’s Black Sea fleet. The city and its forts were built around the northern and southern sides of a harbour. The allied forces landed on the peninsula at Eupatoria, 30 miles to the north of Sebastopol, on 14 September 1854. On 24 September they had advanced to the south side to lay siege to the city. The British took the harbour of Balaklava, on the south of the peninsula, as their supply base. Sebastopol continued to be besieged for the following twelve months.