I hate to differ with brilliant men like George Bush and Barak Obama, who both parrot the "Islam is a peaceful religion" mantra, but I have to. Islam was birthed in murder, beheadings, genocide, slavery, robbery from the beginning. It's founder, Muhammad was a war lord who led his followers in attacks on caravans to plunder the wealth of others. He also lead them in battle to conquer thse that disagreed with his new religion.
I have to conclude that our modern terrorists are as peace loving as their founder Muhammad. Muhammad thought nothing of slaughtering all the men (between 600 and 900 men) who were part of the Banu Qurayzah, a Jewish tribe that lived at Medina and he did not kill but enslaved the women and children of the tribe.
Muhammad did not shrink from leading raids against the caravan of his own tribe (the Quraysh) and killing his kinsmen, when they did not convert and follow him. Muhammad's typical way to deal with the pagan "unbeliever" was to give him an option -- convert, be a Muslim and follow me or die. This form of evangelism proved to be a successful form of evangelism in Arabia and in many other parts of the world.
Islam started as a violent religion. I agree most Muslims are not violent, but Jihad and killing the enemies of Allah are not new, modern distortions of Islam invented by Osama bin Laden. These things are core beliefs that have been a part of Islam since Muhammad and a handful of his followers moved out of Mecca and settled in Medina in 622 AD.