When I first saw this episode some 15 years ago, I did not fully appreciate the significance of Maggie Dawson's Pulitzer Prize winning final photograph that she took just before she was killed in Vietnam on 8th April 1970. That was supposed to be the day when Sam's brother Tom died during an Operation called Lazarus. Operation Lazarus was involved the raid on the Vietcong village to rescue some American POWs, among them a young Naval officer named Al Calavicci (as proven by the photo). But thanks to the treachery by the female Vietcong spy, the prisoners were moved and an ambush was laid for the SEAL's rescue mission. Of course, the older Al's intervention overcame the ambush, saved the marines including Tom Beckett from certain death. But since the prisoners had been moved and so could not be rescued, Operation Lazarus was a failure.
If one thinks about it, Al in his real time guise as Rear Admiral Albert Calavicci would have known (without Ziggi's help) that had Operation Lazarus succeeded, he, Al, would have been rescued with the others. This would have meant that he did not become MIA and would have eventually gone back to his beloved wife Beth - something that he wanted more than anything else in the world. Al would have known this in the previous episode when Sam mentioned the date of his brother's death, but he selflessly refrained from telling Sam about his own involvement in Operation Lazarus and thereby foresook his own freedom and married life to save Sam's brother.
But that's not all. If Lazarus had been successful and Al had returned to his wife, it is likely that he would have setteled down happily and raised a family with her (knowing his love of kids). Under those circumstances, it is unlikely that Al would have thrown himself as ruthlessly into his Naval career as he actually did on the way to becoming an Admiral. This might have meant that Al would never have risen high enough in the Navy to get the sort of clearance that project Quantum Leap required and so might never have met Sam Beckett. Since Sam & Al are equally important to Quantum Leap, it follows that the project may never have happened if Al had been rescued on the battlefield that fateful day!