About Warden’s line to the women porters, "I had to do it! They might have been taken alive!," which has caused a lot of confusion:
The line only makes sense if "they" refers to the other members of his commando team, Joyce and Shears. And it is plural, so it refers to both of them. It does not refer to Nicholson or anyone else.
For the statement to make sense, it is NOT necessary that Warden have actually killed Joyce and Shears with the mortar. We know that Joyce is dead and Shears is dying or dead, but at his distance Warden has no way of knowing if they are dead or alive, all he knows is that they have been shot down by the Japanese.
The statement only makes sense if Warden directed the mortar at Joyce and Shears. In fact, he does. This is subtle. The first mortar shot is directed toward the Japanese soldiers coming to reinforce Nicholson. But the second is directed further downstream, closer to where Joyce and Shears are lying. What the audience sees is that it knocks over Nicholson and another Japanese soldier. (The audience is watching Nicholson, wondering whether he will try to press the plunger himself, and whether he will make it.) What the women see is that Warden directs the shot at his two fallen comrades. Warden has entirely lost interest in the bomb, he just wants to make sure no member of the team is taken alive. "Madness" indeed. And the move was apparently effective. If you look carefully, you'll see that before the second mortar shot, Shears is still moving in the water. After the shot, he is still.
So the statement makes sense. But cinematographically it is subtle, too subtle. You have to fault to directors for leaving audiences confused. The second shot should have landed closer to Joyce and Shears and more visibly disturbed their bodies.