Seljuks, according to Wikipedia, expanded as far as Baghdad. This to me makes this song clearly about the Iraq war, and the framing of the Iraq war as a holy war against Islam (infidels). 'That lead the noble to the east to fight the heathens...' Noble = noble cause, also nobility or King Bush, aka King George. 'For you must enter a room to destroy it' we went into Iraq and it's now essentially decimated. 'Call of the righteous man' to be Christian is to support Bush. 'The reason he must attain' look at the Downing Street Memos where the intelligence was fixed around the policy. I could go on, but this is yet another example of SOADs beautiful use of metaphor and double entendre in its lyrics!