On May 22, Prince Menshikov left Constantinople. On the 31st, Russia issued an ultimatum to Turkey. A declaration was issued stating that the Orthodox Church in Turkey was to be protected, and that Russia would oversee Turkey's occupation of the Danube principalities of Wallachia and Moldavia under the Treaty of Adrianople. In order to cheer up the Sultan and warn Russia, on 13 June the combined British and French fleet sailed into the Gulf of Besiga, which, instead of deterring Russia, deeply provoked it. On July 2, Russian troops crossed the Prut River and occupied Wallachia and Moldavia. On October 5, Turkey declared war on Russia, and war broke out. From the beginning of the war, the war showed a strong political significance, which will continue until the end of the war.

Throughout October, the Russian and Turkish armies were engaged in strategic maneuvers in order to gain an advantage over their opponents in the lower Danube, and on 28 October the Turkish field commander Omar Lutfipasha successfully crossed the Danube with a wide frontal on the south bank of the Danube.

On 4 November, the Turkish army defeated the hurried Russian army at Ortricha. Replenishment is an important issue for both sides. The Balkan theater was far from Russia's political center, and despite Russia's experience of many wars against Turkey, supplies remained the main problem limiting the movement of Russian troops. For Turkey, although Constantinople was close to the battlefield, the Balkan Mountains and the rebellion of the local population made transportation difficult. The Danube River shipping is well developed, and the use of sea transportation has become an inevitable choice for both sides to replenish supplies. The struggle for supremacy in the Black Sea is particularly important.

On 27 November, a small Turkish fleet arrived at the port of Sinop. The commander of the Turkish fleet ordered his subordinates not to open fire first. Soon he spotted six Russian wooden-hulled battleships cruising outside the harbor. He sent an urgent request for reinforcements, but nothing was heard. The Russian battleships, which arrived from Sevastopol a hundred miles away, belonged to the Russian Black Sea Fleet and were commanded by Vice Admiral Pavel Stepanovich Nakhimov.

On the morning of November 30, the Russian fleet entered Sinop Bay and demanded that the Turkish fleet raise the white flag and surrender, the Turkish commander refused to surrender and ordered the opening of the cannon, which was opened a few minutes later by the Russian battleships. When the morning ended, the Russian fleet was completely victorious. Seven Turkish frigates and two light cruisers (both wooden-hulled) were sunk, and the Turkish army suffered 3,000 casualties. It was the last glory of the wooden sail battleship and the last glory of the Russian Black Sea Fleet, and this naval battle went down in history as the last large-scale engagement of the era of the sailing fleet. Although Russia already has ironclad ships, they are mainly concentrated in the Baltic Sea, and there are only three ironclad ships in the Black Sea Fleet, and Nakhimov is ready to leave it to Britain and France as a backhand, while the Ottoman ironclad ships are concentrated in the Dardanelles to blockade the strait, so it is not as big as the outside world thinks.

On January 4, 1854, the British and French fleets entered the Black Sea to escort the Turkish convoy. The size of the fleet is impressive. The British fleet had 11 major warships, while the French fleet had 14 and was armed with more broadside guns, for a total of 8 warships with more than 100 gunwales (5 for France and 3 for the British). The battleships of the Anglo-French fleet were driven by a mixture of sails and steam, and the maneuverability advantage was very obvious. A day later, the Turkish army defeated the Russian offensive at Sitat, which was a wing of the Russian army.

On 6 February, Russia announced the severance of diplomatic relations with Britain and France in response to the combined Anglo-French fleet sailing into the Black Sea. On the 10th, the British peace delegation arrived in Russia for a final diplomatic effort and met with the Tsar. The two sides were very divided, and the Tsar feared war with Britain and France, but was unwilling to back down, and Nikolai told the British envoy: "Do not threaten me with war, and I can rely on Berlin and Vienna." In order to warn Britain and France that they could once again provoke a major war in Europe. However, the Holy Alliance has long since become detached. Prussia had long complained about Russia's protection of Austria in the Austro-Prussian dispute in 1850, and it was not going to take advantage of the Balkans, an issue in which it had no interest in itself. Austria was even more inscrutable, and Nicholas I could never have imagined the betrayal of Austria a few months later.

On 23 February, the first British Army ships went to Turkey. On 27 February, Britain and France issued an ultimatum to Russia to withdraw from Wallachia and Moldavia by 30 April. The tsar ignored it. On March 12, Britain and France formed an alliance with Turkey. On 19 March, the French Army also boarded a ship for Turkey. A day later, the Russian army crossed the Danube. France declared war on Russia on March 27, Britain on March 28, and the Chinese Empire followed on March 29. At that time, the three major powers appeared on the stage together and declared war on Russia, and the war expanded.

On March 30, just after the declaration of war, the combined fleet of Britain and France broke out in the sea outside the Russian naval port of Sevastopol in Crimea, the first ironclad battle in European history. In the face of the huge steam ironclad fleet of Britain and France, there were only three ironclad ships, most of which were still sail fleets, although the Russian Black Sea Fleet fought stubbornly, but the defeat was doomed, and finally the three crappy ironclad ships of Russia were all sunk, and the British and French fleets won a complete victory, and the Russian Black Sea Fleet was completely annihilated. The news soon reached London and Paris, where public opinion quickly heated up (in England, the Battle of Sinop was portrayed as the Sinop Massacre) and public opinion in both countries demanded further action from the government.

On 5 April, British troops landed at Galapoli. This was where the coalition battle plan was born. 60,000 British and French troops landed on the Crimean Peninsula with the cooperation of the navy, and took the Russian naval base Seva Potor Fortress within 6 weeks. This was a limited goal, which was to completely eliminate the Russian presence of the Black Sea Fleet and to put an end to Russian superiority in the Black Sea. This was in line with the wishes of England, and for France, the war itself served its purpose.

The British Army's participating units consisted of 4 infantry divisions, 1 light infantry division and 1 cavalry division. The entire division is around 6,000 people. The participating units of the French Army were 4 infantry divisions and 2 cavalry brigades. The establishment was similar to that of the British army. According to the technical level of artillery at that time, the approach of the French army was more adapted to the needs of actual combat. The status of cavalry in the French army was greatly reduced compared to the Napoleonic era, and the new mini rifle made the cavalry assault power reduced, so the French army rarely used large cavalry regiments. The commander of the British army was Baron Raglan. An approachable aristocrat. The commander of the French army was Marshal Armand-Jacques Leroy de Saint-Arnault. The French Revolution created a new generation of French.

On 20 April, Russia suffered its biggest blow since the start of the war, and Austria declared its neutrality and secretly formed a defensive alliance. The reasons for neutrality were obvious, but the tsar did not see this. The Holy Alliance failed at the most critical time, leaving him frustrated and angry. As if to pour another handful of salt into the Tsar's wounds, the British and French fleets shelled Odessa on April 22, indicating that Britain and France were really prepared for a war with Russia. On 3 June, Austria completed its deployment, placing 80,000 troops on Hungary's borders with Wallachia and Moldavia, and issuing an ultimatum to Russia for the immediate withdrawal of its troops from the two principalities. On 14 June, Austria signed a treaty with Turkey, in which Turkey agreed to Austrian occupation of the two principalities until the end of the war. Austria's imprudence and greed completely destroyed the Russian-Austrian friendship that had existed since 1815, and relations between the two countries have never been better. The tsar at this time felt shameful betrayal, and he finally understood that he had fallen into a terrible trap. The war was exactly what he had expected, with more and more enemies, and the betrayal of his friend and brother, Emperor Franz Joseph I, and the news of the situation in the Far East made him lose faith in the war, but the war was still going on. The Austrian Emperor was busy marrying Princess Sissi from Bavaria, a paradise and a hell