From Charles Moore here:
'Ayatollah Khomeini ... said “Islam is politics”. He meant that Islam tells you how to rule, and therefore any unIslamic way of ruling is illegitimate. ... Khomeini was a Shia, but a similar way of weaponising the faith was also developed in Sunni Islam. It stands behind organisations like the Muslim Brotherhood . . .. It rests not only on an interpretation of the words of God allegedly spoken through the mouth of his Prophet, but on a tale of grievance. In this tale, bad people – colonial powers, Christians, Jews, America, “hypocrite” Muslim monarchs – destroyed the right rule of true Islam (the caliphate) and humiliated the faithful. This world-view is known as “Islamism”. Islam itself is related to Islamism as patriotism is related to nationalism, the former being based on love of something, the latter on hatred of something else. Islamism validates resentment. Its emotional appeal is like that of communism and fascism, but stronger, because it promises heaven to those who commit its violent acts on earth.'