Disunite (verb)

1. Break up the unity or unity of (something); cause to separate or become separated into pieces.
2. End the unity or unity of (a group of people); cause to divide.

Origin:

Late middle english: from old french desunir, from latin dis- (expressing reversal) + unire 'to unite'.

Examples:

1. The company was disunited by the decision to lay off hundreds of employees.
2. The family was disunited by the news of the grandfather's death.
3. The country was disunited by the civil war.
4. The group of friends were disunited by the argument about who should lead the project.
5. The political party was disunited by the decision of the leader to step down.