Some quotes from the Hadith which are the collected sayings of Mohammed, and some quotes from Muslim web sites.
“The sword is the key of heaven and hell. A drop of blood in the cause of Allah — a night spent in arms [war] — is of more avail than two months of fasting and prayer. Whosoever falls in battle, his sins are forgiven, and at the day of judgment, his limbs shall be supplied by the wings of angels and cherubim.”
In the Muslim viewpoint, the world is divided into two regions — those areas controlled by Islam, called Dar al-Islam (meaning the House of Islam) and those called Dar al-Harb (the House of War). The Koran commands Muslims to fight non-Muslims until they exterminate all other religions, leaving Islam as the one and only religion in the world (Suras 2:193 and 8:39). Muhammad is quoted in the Hadith as saying, “I have been ordered to fight with the people until they say, none has the right to be worshiped but Allah” (Hadith 4:196).
Regarding terror, Allah orders Muslims to terrorize non-Muslims on his behalf: “Strike terror (into the hearts of ) the enemies of Allah and your enemies” (Sura 8:60). Allah then assures his followers that he will assist them: “I will instill terror into the hearts of unbelievers. Smite them above their necks and smite all their finger-tips off them. It is not you who slay them, it is Allah” (Sura 8:12, 17).
While it is true that in many places where Muslim armies went to liberate people or the land, they did carry the sword as that was the weapon used at that time. However, Islam did not spread by the sword because in many places where there are Muslims now, in the Far East like Indonesia, China, and many parts of Africa, there are no records of any Muslim armies going there. For instance, Muslims ruled India for over 1,000 years and yet only 15% of Indians are Muslims. If the ‘sword’ had been used, the statistics would have been otherwise. Despite 1,400 years Muslim presence in the Arab world, some 10% of all Arabs are Christians. (islam-usa.com)
[What this shows is that the sword was used to conquer most of the world and then pressure was applied to the people for them to convert. Of course the rulers did not kill everyone that did not convert, that would have been nearly impossible to accomplish. The rulers just taxed the non-muslims and discriminated against them while giving great favor to those that converted.]
All Muslims are all well aware that they were the superior military and cultural force in the world for centuries, and the reversed situation in the modern ages hurts the pride of Muslims….