Pipes says to aid whichever side is losing so as to prevent either side from winning, and to prolong the conflict.
It’s going to require a fine balancing act to supply everyone with just enough weapons so they can all shoot themselves in the foot.
That’s why Russian and Iranian participation is so useful — no need to switch sides, or for matter, to spend much at all. We need only keep the humanitarian aid going, and surreptitiously snuff imam/mullah activity in the refugee camps, such that the noncombatants only have eyes for us.