John Robb says that the death of King Abdullah gives ISIS a golden opportunity to take Mecca and Medina for the caliphate. Here’s how:

• ISIS would pivot forces from Syria and Iraq for a push south (indications are that this is apparently already underway), and then use these forces to rapidly overwhelm numerous border posts to create widespread confusion within the Saudi security forces.  If done correctly, the rapid advances of black flags will cause a mass rout that will yield significant equipment and a considerable number of new jihadis (as troops flip to join the ISIS jihad).
• Simultaneous with the drive south, cells of ISIS jihadis and lone sympathizers will activate across the Kingdom, causing disruption and confusion.  With this, lines of authority and communication within the kingdom will begin to break down.
• The advancing jihad will connect with local forces along a massive front moving south, jumping from city to city.  The speed of this will depend on how willing the population is to accept ISIS.  However, since Saudi Arabia has already indoctrinated its population with a religious ideology that is sympathetic to ISIS, the speed of the advance may be very rapid.

I have no idea how plausible this is, but I find it hard to imagine that Saudi soldiers would be all that loyal to the royal family. Read the whole thing. 

UPDATE: An earlier Robb piece worth reading. Did you know ISIS earlier this month killed a top Saudi general? I didn’t. Robb says:

The Saudis are vulnerable.  The attackers knew exactly when the general was going to be at the outpost.  This tells us that the Saudi military is rife with ISIS sympathisers and/or active members.  If so, the Saudi military may melt away when facing jihadis (or switch sides) in the same way 30,000 Iraqi troops did early last year a couple of hundred miles to the north.