.But both Christianity and Islam have always stated that they followed the One God that created everything and all people
I don't think they thought that way during the crusades...
Most mainstream Muslims would generally agree they worship the same God that Christians — or Jews —worship. ... Christians, however, believe in a triune God: God the father, God the son (Jesus Christ) and the Holy Spirit. And many evangelicals will say that means Muslims and Jews do notworship the same god as Christians.Dec 20, 2015
http://www.npr.org/2015/12/20/460480698/do-christians-and-muslims-worship-the-same-god