In the summer of 1823, Alexander I issued a secret manifest excluding Constantine from the order of succession and making Nicholas heir presumptive to the throne.
Historians argue as to whether or not Miloradovich had been formally made aware of Alexander's decision.
Only three men – Aleksey Arakcheyev, Alexander Golitsyn, and Archbishop Filaret – definitely knew the contents and whereabouts of the manifest; neither Constantine nor Nicholas knew the whole story.

On December 9 [O.S. November 27] 1825, when news of Alexander's death in Taganrog reached Saint Petersburg, Miloradovich bullied Nicholas into pledging allegiance to Constantine, who was then living in Warsaw as viceroy of Poland.
Golitsyn arrived at the palace later and announced the terms of Alexander's manifest, but Miloradovich persuaded the State Council that Nicholas was aware of it and that his pledge of allegiance to Constantine was effectively an act of abdication.
Miloradovich then sent a messenger to Moscow with two instructions: to pledge allegiance to Constantin and to keep the original of Alexander's manifest secret and locked away.
Faced with the question, "What if Constantine holds to his resignation?",
Miloradovich allegedly responded, "When one has one hundred thousand bayonets in one's pocket, it is easy to speak with boldness".

Correspondence between Saint Petersburg and Warsaw took two weeks, during which Miloradovich acted as de facto interrex and regularly assured Nicholas that "everything is quiet".
Constantine firmly refused to reign and blessed his brother's accession to the throne, but for a while the hesitant Nicholas took no action.
On the morning of December 24 [O.S. December 12], Nicholas received detailed reports of the brewing Decembrist revolt from Diebitsch and Chernyshov, and discussed the matter with Miloradovich and Golitsyn.
According to Nicholas himself, the evidence was overwhelming.
Miloradovich promised to mobilise all police resources but did nothing or, according to Korf, his "investigations remained completely fruitless.
His researches had not discovered one person on whom suspicion could reasonably fall".

The actions of Miloradovich during the interregnum were highly controversial and provoked fringe conspiracy theories placing him at the top of the Decembrist rebel ring.
Mainstream historians provide different explanations of his motives, none of which supports the theory of "Decembrist Miloradovich":
Mikhail Safonov suggested that there were three contenders for the throne: Constantin, Nicholas and their mother Maria Fyodorovna.
Miloradovich supported Maria but in public he aligned with Constantine and later with Nicholas.
A similar version has been fictionalised by Igor Bunich.

Yakov Gordin suggested that Miloradovich acted as an independent dictator, using Constantine merely as a front.

Andreeva supports a toned-down variation of Gordin's suggestion: that, regardless of Alexander's manifest, Miloradovich acted in good faith, supporting what he thought was the legitimate solution to a crisis.
In the summer of 1823, Alexander I issued a secret manifest excluding Constantine from the order of succession and making Nicholas heir presumptive to the throne. Historians argue as to whether or not Miloradovich had been formally made aware of Alexander's decision. Only three men – Aleksey Arakcheyev, Alexander Golitsyn, and Archbishop Filaret – definitely knew the contents and whereabouts of the manifest; neither Constantine nor Nicholas knew the whole story.
On December 9 [O.S. November 27] 1825, when news of Alexander's death in Taganrog reached Saint Petersburg, Miloradovich bullied Nicholas into pledging allegiance to Constantine, who was then living in Warsaw as viceroy of Poland. Golitsyn arrived at the palace later and announced the terms of Alexander's manifest, but Miloradovich persuaded the State Council that Nicholas was aware of it and that his pledge of allegiance to Constantine was effectively an act of abdication. Miloradovich then sent a messenger to Moscow with two instructions: to pledge allegiance to Constantin and to keep the original of Alexander's manifest secret and locked away. Faced with the question, "What if Constantine holds to his resignation?", Miloradovich allegedly responded, "When one has one hundred thousand bayonets in one's pocket, it is easy to speak with boldness".
Correspondence between Saint Petersburg and Warsaw took two weeks, during which Miloradovich acted as de facto interrex and regularly assured Nicholas that "everything is quiet". Constantine firmly refused to reign and blessed his brother's accession to the throne, but for a while the hesitant Nicholas took no action. On the morning of December 24 [O.S. December 12], Nicholas received detailed reports of the brewing Decembrist revolt from Diebitsch and Chernyshov, and discussed the matter with Miloradovich and Golitsyn. According to Nicholas himself, the evidence was overwhelming. Miloradovich promised to mobilise all police resources but did nothing or, according to Korf, his "investigations remained completely fruitless. His researches had not discovered one person on whom suspicion could reasonably fall".
The actions of Miloradovich during the interregnum were highly controversial and provoked fringe conspiracy theories placing him at the top of the Decembrist rebel ring. Mainstream historians provide different explanations of his motives, none of which supports the theory of "Decembrist Miloradovich":
Mikhail Safonov suggested that there were three contenders for the throne: Constantin, Nicholas and their mother Maria Fyodorovna. Miloradovich supported Maria but in public he aligned with Constantine and later with Nicholas. A similar version has been fictionalised by Igor Bunich.
Yakov Gordin suggested that Miloradovich acted as an independent dictator, using Constantine merely as a front.
Andreeva supports a toned-down variation of Gordin's suggestion: that, regardless of Alexander's manifest, Miloradovich acted in good faith, supporting what he thought was the legitimate solution to a crisis.
Mikhail Miloradovich