Comment: If they are serious: US

(See in situ)

If they are serious: US

If they are serious:
US strikes Syria.
Iran strikes at Israel(although with all the defences, I doubt any missles would get through)
China and Russia do something towards the US(may not be striking back, but more likely shut down of trade or something)
US and Israel strike at Iran in retaliation
China and Russia likely strike at the US this time(or they are complete pushovers)
Things likely go to hell

To climb the mountain, you must believe you can.