Don't bother with the tedious procedures of recruitment, just head straight for enemy hq with some dynamite and introduce them to Mr. Big explosion. Also if you start every game by clicking the mouse in exactly the same place on the start screen, every game will be set up identically.
Invulnerablity against missiles: Whether you are skiing or driving a now-buggy, the moment you hear the missile being launched, stop immediately and begin to turn around. Keep turning on the spot. The missile will narrowly miss you then come back and keep pace alongside you for a while until it finally speeds off to clobber someone else not so smart.
Invulnerablity against mortars: Watch for the bomber. It will always come over the horizon in front of you. If you are stopped, wait until it is approximately half way to you (otherwise it may be able to dodge your missile) then blast it. If you are moving fast blast it the moment it appears over the horizon. If the bomber does manage to drop mortars turn 90 degrees quickly and speed off.