Eliezer's point is that, given a certain decision theory (or, failing that, a certain set of incentives to precommitment), rational soldiers could in fact carry out even suicide missions if the tactical incentives were strong enough for them to precommit to a certain chance of drawing such a mission.

This has actually come up: in World War II (citation in Pinker's "How the Mind Works"), bomber pilots making runs on Japan had a 1 in 4 chance of survival. Someone realized that the missions could be carried out with half the planes if those planes carried bombs in place of their fuel for the return trip; the pilots could draw straws, and half would survive while the other half went on a suicide mission. Despite the fact that precommitting to this policy would have doubled their chances of survival, the actual pilots were unable to adopt this policy (among other things, because they were suspicious that those so chosen would renege rather than carry out the mission).

I think Eliezer believes that a team of soldiers trained by Jeffreysai would be able to precommit in this fashion and carry the mission through if selected. I think that, even if humans can't meet such a high standard by training and will alone, that there could exist some form of preparation or institution that could make it a workable strategy.