Not cutting down on lethality in a tabletop RPG

Character death is not something well seen in RPGs, nobody wants to drop out of the session because his or her character died. Yet it is tough to roleplay a modern warfare game, specially one centered around black ops, without considering that your character won't make it back. Worse yet, that he or she can't make it back or must not make it back.

When the mission is more important than the soldier is your roleplaying more important than your character?

Making things extremely lethal has not only opened the doors for new ways to resolve combat and make encounters survivable through skill and tactics. High lethality is also opening the door to new aspects of roleplay which are more realistic and seldom explored by many. So far it has added a greater importance to planning, speed and resolve over everything else. Retreat, cover and redeployment have become common place when previously stand and deliver strategies were used, legacy of some other less lethal games. Now comes the question of paying the ultimate price. Are players up to the task?

Had an interesting conversation last night with +Jonathan Henry and +Keith Bailey and Jonathan brought up the issue of the obligation to complete the mission. Will players sacrifice their character for the benefit of other player's characters? Will the do so for the mission? Will all players sacrifice their characters if that is what it takes to succeed?

If so, how does this affect character development? Would you as a player invest lots of time in developing a character that might not make it through the first session? Wouldn't this make the game an eternal succession of one shots?.

Now lets draw a line between overdeveloping a character and delaying the "getting down to play" vs overdeveloping a character that may die soon. I don't want to delay the game, and that is not where my question is going. The character may not die, living on for many more sessions only to arrive at this one moment when they all must die to succeed. Would your investment in your character stop you from succeeding in the mission? Would you sit down and play again?