Belarus is a landlocked country in Eastern Europe bordered by Russia north and east, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Belarus has been a member of the United Nations since 1945 and the Council of Europe since 1991. The country is the site of the Chernobyl nuclear disaster, which occurred in 1986.

Belarus was a republic of the Soviet Union from its inception in 1922 until its dissolution in 1991. During that time, it was known as the Byelorussian Soviet Socialist Republic (BSSR). After the BSSR was dissolved, Belarus became an independent country. Belarus has a population of 9.4 million people (as of 2016), and its capital and largest city is Minsk. The official language is Belarusian, and Russian is also widely spoken. Belarus is a unitary state, and its current president is Alexander Lukashenko, who has been in office since 1994.

The Soviet Union annexed a number of countries during its existence, but Belarus was not one of them. There are a number of possible explanations for this.

First, Belarus was not strategically important to the Soviet Union. It is landlocked and is not adjacent to any major body of water. Additionally, its population is relatively small, and it does not have any major natural resources.

Second, Belarus was not economically important to the Soviet Union. Its economy was primarily based on agriculture and was not a major industrial or commercial center.

Third, Belarus was not ethnically homogeneous. Unlike many other Soviet republics, Belarus had a significant population of ethnic Poles and Jews. This made it difficult to integrate Belarus into the Soviet Union.

Fourth, Belarus had a history of resistance to Russian rule. This was most evident during the 19th century when Belarus was part of the Russian Empire. A number of uprisings and rebellions occurred during this time, and the Belarusian nationalist movement emerged.

Finally, Belarus was not annexed by the Soviet Union because it was not in the Soviet sphere of influence. At the time of the Soviet Union's collapse, Belarus was part of the Soviet Union's 'outer empire' and was not considered to be part of the Soviet Union proper.

While Belarus was not annexed by the Soviet Union, it did become a close ally of the Soviet Union after its independence. Belarus joined the Commonwealth of Independent States (CIS) in 1991 and has remained a member of the CIS since then. Additionally, Belarus has close economic and political ties with Russia.