Formation of USSR:
The Union of Soviet Socialist Republics (USSR) was formed on December 30, 1922. It came into existence after the Bolsheviks, led by Vladimir Lenin, emerged victorious in the Russian Revolution and established the Russian Soviet Federative Socialist Republic (RSFSR) as the first socialist state in the world. The RSFSR served as the foundation for the creation of the USSR.

All-Russian Congress of Soviets:
The All-Russian Congress of Soviets was a key event in the Russian Revolution and the subsequent formation of the USSR. It was a gathering of representatives from workers, peasants, and soldiers' councils known as soviets, which had sprung up across Russia in the wake of the February Revolution in 1917. The Congress consisted of delegates elected by these soviets and aimed to establish a new government structure that would replace the Provisional Government.

Key Events:
1. February Revolution: In February 1917, mass protests and strikes erupted in Petrograd (now St. Petersburg) due to food shortages, high prices, and discontent with the ongoing World War I. The protests led to the overthrow of the Russian monarchy and the establishment of a Provisional Government, which shared power with the Petrograd Soviet.

2. October Revolution: The October Revolution, also known as the Bolshevik Revolution, occurred in October 1917. The Bolshevik Party, led by Lenin, seized power from the Provisional Government. The Bolsheviks' slogan of "Peace, Land, and Bread" resonated with the masses, and they gained support from the soviets.

3. All-Russian Congress of Soviets: The Congress convened in Petrograd in January 1918 and was dominated by Bolshevik delegates. It declared the establishment of the RSFSR as the new government, marking the formal beginning of the Soviet Union. The Congress also approved the Decree on Peace, which called for an end to World War I, and the Decree on Land, which redistributed land to the peasants.

4. Formation of the USSR: Over the next few years, the Bolsheviks consolidated their power and expanded their control over other regions of Russia. In December 1922, the First Congress of Soviets of the USSR was held, and the Treaty on the Creation of the USSR was signed, officially establishing the Soviet Union.

Overall, the formation of the USSR was a result of the Russian Revolution and the subsequent consolidation of power by the Bolshevik Party. The All-Russian Congress of Soviets played a crucial role in this process by providing a platform for the representation and decision-making of the various soviets across Russia.