And here are some quotes from the Koran and other authoritative sources that back up what I have been saying:

Qur'an:9:88 "The Messenger and those who believe with him, strive hard and fight with their wealth and lives in Allah's Cause." 
Qur'an:9:5 "Fight and kill the disbelievers wherever you find them, take them captive, harass them, lie in wait and ambush them using every stratagem of war." 
Qur'an:9:112 "The Believers fight in Allah's Cause, they slay and are slain, kill and are killed." 
Qur'an:9:29 "Fight those who do not believe until they all surrender, paying the protective tax in submission." 
Ishaq:325 "Muslims, fight in Allah's Cause. Stand firm and you will prosper. Help the Prophet, obey him, give him your allegiance, and your religion will be victorious." 
Qur'an:8:39 "Fight them until all opposition ends and all submit to Allah." 
Qur'an:8:39 "So fight them until there is no more Fitnah (disbelief [non-Muslims]) and all submit to the religion of Allah alone (in the whole world)." 
Ishaq:324 "He said, 'Fight them so that there is no more rebellion, and religion, all of it, is for Allah only. Allah must have no rivals.'" 
Qur'an:9:14 "Fight them and Allah will punish them by your hands, lay them low, and cover them with shame. He will help you over them." 
Ishaq:300 "I am fighting in Allah's service. This is piety and a good deed. In Allah's war I do not fear as others should. For this fighting is righteous, true, and good." 
Ishaq:587 "Our onslaught will not be a weak faltering affair. We shall fight as long as we live. We will fight until you turn to Islam, humbly seeking refuge. We will fight not caring whom we meet. We will fight whether we destroy ancient holdings or newly gotten gains. We have mutilated every opponent. We have driven them violently before us at the command of Allah and Islam. We will fight until our religion is established. And we will plunder them, for they must suffer disgrace." 
Qur'an:8:65 "O Prophet, urge the faithful to fight. If there are twenty among you with determination they will vanquish two hundred; if there are a hundred then they will slaughter a thousand unbelievers, for the infidels are a people devoid of understanding." 

Want more? There's plenty where that came from...