Islam itself is divided into two sects: Shiites and Sunnis and each one of them are also divided to other sects and many have tried to abuse the differences between sects against Muslims.
According to Imam the most significant reason for the colonialists to create division among Muslims is proposing the nationality and ethnicity. Colonialists made Muslims confront each other and even made them their enemies. Imam believed that colonialists make no differences between patriotism which is a very sacred feeling and nationalism which causes contrasts among Muslims and consider them the same to cause hatred among Muslims.(1)
According to Imam what is more dangerous than nationalism is causing disagreements between Shiites and Sunnis and inducing seditious advertisements among Muslim brothers.
Imam Khomeini believed that Superpowers are the reasons for division between Shiites and Sunnis and he has said that:
"We acknowledge that the Shi`ite and Sunni brothers have not been able to create the unity required to confront the infidels and polytheists due to their own fault or some other elements. These hands do not let such unity find reality." (2)
Source: The Unity Architecture, Page: 29