What would u do if Syria waged a war over Israel to get it's land back ?

If Syria attacked Israel an got back all that belong to them? The Israeli can do nothing but only a few air strikes against Syria. Now days Russia is helping Syria an Iran with there military aid. The Israeli is worryed about the possible sell of the Russian S300 anti missile system, If i was Russian i would sold them the newest generation of the S300 the S400. And other anvanice weapons systems an fighters jets.