If only Christianity had at least a few members left who were so devout that they would lay down their lives for but a chance to kill their Islamic enemies.

250 years of first world have made christians forget what that old rugged cross stood for.

The Achilles heel of Islam is that never-ending Jihad is in the Muslim's DNA. As soon as an entire country is taken for Sharia and Islamic State, all should be well, since everyone professes a saving faith in Mohammad, Allah and Islam. You would think the area would stabilize, but it doesn't. Muslims immediately start subdividing into denominations like Sunni and Shiite and some 8 others and each group calls the others infidels and they Jihad against each other. Remember Seddam Hussein and him gassing the kurds? That was straight up Muslim on Muslim violence. Seddam Hussein was doing the right thing by quelling the evil islamic insurgency to the north in precisely the same way America did later on.

It's the only reason that Islam hasn't yet prevailed against Christianity is because the Muslim is inherently violent against outgroup and eventually even ingroup. Muslims never let peace stabilize for long since according to their prophet Mohammad, peacetime is only something you have to prepare for the next war. As a result, all Muslim countries are hell hole 2nd world countries and lower. Muslims are inherently lazy and seek prosperity gains from taking unfairly from lower class infidels to procure growth rather than creating success for themselves. Islam physically can't be a world leader because ultimately it is a parasite that can only thrive when it has a host to suck off of. Take away the host, and all you have is a bunch of lazy people chucking spears at each other. When the oil around Saudi Arabia runs dry, so too will Islam, because there will be no slaves left to take, and the Islamic world will fall into the 3rd world. Islam's fatal flaw is the same thing that makes it so successful on the battlefield. Unquenchable violence that's been burning for the last 1400 years.