4 sentences

1. 苏联于1991年解体。

   Sū​lián yú yī​jiǔ​jiǔ​yī​nián jiě​tǐ.

   The Soviet Union dissolved in 1991.

   Source: Dong Chinese Dictionary

2. 冷战在1991年结束了。

   Lěng​zhàn zài yī​jiǔ​jiǔ​yī​nián jié​shù le.

   The Cold War ended in 1991.

   Source: Dong Chinese Dictionary

3. 苏联在1991年正式解体。

   Sū​lián zài yī​jiǔ​jiǔ​yī​nián zhèng​shì jiě​tǐ.

   The Soviet Union officially disintegrated in 1991.

   Source: Dong Chinese Dictionary

4. 前苏联在1991年正式解体。

   qián Sū​lián zài yī​jiǔ​jiǔ​yī​nián zhèng​shì jiě​tǐ.

   The former Soviet Union officially dissolved in 1991.

   Source: Dong Chinese Dictionary