What's the Key Aspect of the Baltic Fleet?

In 1855, Sevastopol falls to a very well organized French infantry assault. The Russians retreat abandoned the city and the war is signed off in March next year. Russia has become bankrupt, economically dysfunctional and is unable to continue fighting. Britain builds an enormous fleet to attack St Petersburg and the island of Kronstadt which is a primary defense system. And by the time we get to the breakup of Baltic ice in late March, 1856, the Royal Navy has 250 gunboats,. It's going to sit down off St Petersburg and destroy all the fortifications and hold the city at risk. This is how the Russians are brought to peace. They have no money. They're losing friends.