Ascension to the throne
Alexander I's unexpected death in southern Russia on Dec. 1, 1825, led to a dynastic crisis. Because Alexander I had no direct male successor, Constantine was next in line for the throne. But the heir presumptive had married a Polish woman not of royal blood in 1820 and renounced his rights to the crown. Nicholas was thus to become the next ruler of Russia, the entire matter being stated, in 1822, in a manifesto confirmed with Alexander I's signature.
But the manifesto remained unpublished, and Nicholas questioned the legal handling of the whole issue and the reaction in the country, which expected Constantine to succeed Alexander. In any case, Constantine and the Polish kingdom of which he was commander in chief swore allegiance to Nicholas, but Nicholas, the Russian capital, and the Russian Army swore allegiance to Constantine.
It was only after Constantine's unyielding re-affirmation of his position and the resulting lapse of time that Nicholas decided to publish Alexander's manifesto and become emperor of Russia. On Dec. 26, 1825 (Dec. 14, O.S.), when the guard regiments in St. Petersburg were to swear allegiance for the second time in rapid succession, this time to Nicholas, liberal conspirators staged what came to be known as the Decembrist Rebellion.
Utilising their influence in the army, in which many of them were officers, they started a mutiny in several units, which they entreated to defend the rightful interests of Constantine against his usurping brother. Altogether some 3,000 misled rebels marched in military formation to the Senate Square in the heart of the capital. Although the rebellion had failed by nightfall, it meant that Nicholas I ascended the throne over the bodies of some of his subjects and in actual combat with the dreaded revolution.
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