About 500 miles and that is a very very very long way if you have adequate air power to kill the nice neat columns of invading forces aside from ground forces that can and will fight. This "aint gonna" happen and I am not a fan of Saudi;
I don't have a strong opinion, but the Saudi military isn't the greatest. They have been relying on us, and now that we are leaving. they are on their own. They have been trying to build a sunni coalition, but that does not seem to have been successful. I guess the current fighting in Yemen is giving them experience in battle, but it doesn't seem that they are clearly winning, especially if they are now having to fight inside Saudi Arabia.