The Siege of Mikhailovsky (Adyghe:  Михайловски Къэуцухьэ; Russian: Оборона Михайловского укрепления) took place on 3 April 1840 during the Russo-Circassian War.

Unwilling to accept defeat, Russian soldier Arhip Osipov infiltrated the powder magazine and detonated the explosives, killing himself, the remnants of the garrison, and a significant number of Circassians.

The Russians had been landing and building fortifications on the Black Sea coast of Circassia for a long time.

The Russians began to strengthen their fortifications by making more landings on the Black Sea coast and gained control and gathered a large army.

The Mikhailovsky fortification began to be built in 1837 at the mouth of the Vulan River to establish control over the region.

Therefore, in case of military danger, the Russian garrisons had to rely only on their own forces, without any hope of external help.

[13][23][24] The chief of the Caucasian line, General Pavel Grabbe, wrote in his report:They abandoned their homes and families and took a joint oath that they would not disperse until they had captured all the forts and fortifications along the coastline.Circassian spies, such as Shogen Musa, noted the weak points of Russian fortifications under the guise of trade.

The Poles also helped the Circassians, teaching them the latest European methods of besieging the fortifications.

After the capture of the Lazarevsky and Velyaminovsky fortresses, the Circassians began to prepare for the assault on the Mikhailovsky fortification with new forces.

[13] The Russian garrison of the Mikhailovsky fortification during the assault consisted of the 2nd and 3rd companies of the Black Sea Line Battalion No.

[25] By 22:00 on March 21, the Circassians had surrounded the fortifications from all sides at a considerable distance, their main force hiding in the forest beyond the Vulanom River.

At 4 o'clock on the night of March 21–22, just before dawn, the Circassians began to approach the walls silently from different directions with ladders in their hands.

Noticing that the Circassians were advancing towards the fortifications, a guard immediately reported this to Senior Sergeant H. Komlev.

It was decided to send the infantry militia to the attack a second time, and the cavalry to approach to perform the function of a barrier detachment.

The purpose of this fake attack was to draw the garrison away from the northern and northeastern parts of the fortress, followed by the main forces of the Circassians.

The commander of the 9th company of the Tenginsky regiment, Lieutenant Kraumgold, was shot and stumbled as he ran to the scene shouting "don't be afraid",  and was later "torn to pieces" by the Circassians.

Commander Liko was wounded in the right leg and blood was flowing into his eyes from his severed left eyebrow.

A Russian soldier here, Aleksandr Fyodorov, fought for a long time with a bayonet and rifle butt with about a dozen Circassians.

All the bastions were captured by the Circassians and red victory banners were hung on them while shouting "Allahu Akbar".

DV Rakovic wrote, quoting the words of an eyewitness:There was a terrible noise, everything shook, and a column of smoke rose into the air, full of flames, human corpses, and stones!

On April 11, Lieutenant General NN Rayevsky also received a report on the fall of the Mikhailovsky fortifications and noted: Terrible!