Nicholas I (Nikolai I Pavlovich; 6 July [O.S. 25 June] 1796 – 2 March [O.S. 18 February] 1855) was the Emperor of Russia from 1825 until 1855. 

He was also the King of Poland and Grand Duke of Finland. He is best known as a political conservative whose reign was marked by geographical expansion, repression of dissent, economic stagnation, poor administrative policies, a corrupt bureaucracy, and frequent wars that culminated in Russia's disastrous defeat in the Crimean War of 1853-56. His biographer Nicholas Riasanovsky says that Nicholas displayed determination, singleness of purpose, and an iron will, along with a powerful sense of duty and a dedication to very hard work. He saw himself as a soldier – a junior officer totally consumed by spit and polish. A handsome man, he was highly nervous and aggressive. Trained as an engineer, he was a stickler for minute detail. His reign had an ideology called "Official Nationality" that was proclaimed officially in 1833. It was a reactionary policy based on orthodoxy in religion, autocracy in government, and Russian nationalism

Because of the success of revolutionary resistance, Franz Joseph had to ask for help from the "gendarme of Europe" Czar Nicholas I of Russia in March 1849. Russian armies, composed of about 8,000 soldiers, invaded Transylvania on 7 April 1848. But as they crossed the Southern Carpathian mountain passes (along the border of Transylvania and Wallachia), they were met by a large Hungarian revolutionary army led by Józef Bem, a Polish-born General.

Bem had been a participant in the Polish insurrection of 1830 – 1831, had been involved in the uprising in Vienna in 1848 and, finally, became one of the top army commanders for the Hungarian Republic from 1848 – 1849. When he encountered the Russians, Bem defeated them and forced them back out of the towns of Hermannstadt (now Sibiu, Romania) and Kronstadt (now Brașov) in Transylvania, back over the Southern Carpathian Mountains through the Roterturm Pass into Wallachia. Only 2,000 Russian soldiers made it out of Transylvania back into Wallachia, the other 6,000 troops being killed or captured by the Hungarian Army. After securing all of Transylvania, Bem moved his 30,000–40,000-man Hungarian army against Austrian forces in the northern Banat capturing the city of Temesvár (now Timişoara, Romania).

In June 1849 Russian and Austrian troops entered Hungary heavily outnumbering the Hungarian army. After all appeals to other European states failed, Kossuth abdicated on August 11, 1849 in favour of Artúr Görgey, who he thought was the only general who was capable of saving the nation. However, in May 1849, Czar Nicholas I pledged to redouble his efforts against the Hungarian Government. He and Emperor Franz Joseph started to regather and rearm an army to be commanded by Anton Vogl, the Austrian lieutenant-field-marshal who had actively participated in the suppression of the national liberation movement in Galacia in 1848. But even at this stage Vogl was occupied trying to stop another revolutionary uprising in Galacia. The Czar was also preparing to send 30,000 Russian soldiers back over the Eastern Carpathian Mountains from Poland. Austria held Galacia and moved into Hungary, independent of Vogl's forces. On August 13, after several bitter defeats in a hopeless situation, Görgey signed a surrender at Világos (now Şiria, Romania) to the Russians, who handed the army over to the Austrians.