British and French Intervention
De Redcliffe urged Britain to take a strong line with the support of Palmerston (he argued that Russian forces would back down if strongly opposed) whilst Aberdeen remained cautious. He did not believe that Russia was plotting Turkey's destruction but he was concerned that they would try and take over Constantinople through the Straits (the Bosphorus and Dardanelles that link from the Black Sea to the Mediterranean). Aberdeen's efforts to create a peaceful solution to this were crushed by Russophobia among the public, leading to Liberals and Radicals (MPs who support widespread economic and social change in Britain) to challenge Russian authority. British ships were sent outside the Dardanelles as a gesture of support to the Turks in June, and they soon joined by France. Aberdeen did not trust Napoleon III but cooperating with them to help Turkey could not be escaped. The following month, Tsar Nicholas ordered his troops into Moldavia and Wallachia stating that Russian forces would withdraw when the Turks accepted Menshikov's demands. Turkey did not give up, especially with the aid of Britain and France.
The Vienna Note
Austria attempted to defuse the crisis by organising a conference in Vienna hoping to find an solution that would satisfy the Tsar's honour yet safeguard Turkey's integrity. The diplomats proposed that the Sultan should make a few acknowledgements to the Tsar and consult Russia and France about his policy towards the Ottoman Christian. Russia in return would leave the Principalities (Moldavia and Wallachia). In August, Russia accepted this note but the Sultan with the backing of de Redcliffe insisted on some amendments that were rejected by the Tsar.
The radical MPs believed that Russia's demands were reasonable. Orlando Figes claims that this war was the first in history launched to appease British public sentiment- media-inspired paranoia about Russia - rather than in pursuit of any coherent national purpose. In actual fact Britain went to war with the purpose of thwarting Russian plans to dismantle the Ottoman Empire and seize Constantinople (this would have threatened British naval supremacy in the eastern Mediterranean). Others blame British responsibility on the divided councils in Aberdeen's government, the PM was pacific and anti-Turkish while Palmerston was bellicose (willing to fight) and anti-Russian. If Britain had had a more consistent line - hard or soft - was would have been averted.
Tsar Nicholas was responsible for a series of miscalculations which led to confrontation with Turkey. His exaggerated sense of honour led him to reject several diplomatic attempts to resolve the crisis in 1853-1854.
The crisis was initiated by raising the issue of the Holy Places. Napoleon III can be accused of playing to the gallery at home regardless of the likely reprecussions.
They were not innocent although they do appear to be the hapless victims of great power politics. Western support presented them with an opportunity to stand firm against Russia