I am no expert on the subject, but quickly researching, it seems that during the Black September in Jordan, Syria actually did send military forces in Jordan. The Jordanian King asked Britain and the USA for help, and as a result, Israel preformed 'mock air strikes' again Syrian columns. Syria backed out of Jordan at this point. However, if Israel is unwilling to go into a war at this point, what happens? Would Syria beat Jordan in a war? What I find interesting is how this could change the regional dynamic-it could create a Jordanian-Israeli alliance, which could be achieved if Israel does enter the war.