Taken from here. Note that whether torture can work is not the same question as whether we should do it.
“Happened all the time. At the Battle of Midway, two American fliers, whose planes had been shot down near the Japanese carriers, were pulled out of the water and threatened with death unless they revealed the position of the American carriers. They did so, and were then promptly executed. Later, at Guadalcanal, the Japanese captured an American soldier who told them about a planned offensive – with that knowledge the Japanese withdrew from the area about to be attacked. I don’t why he talked [the guy didn't survive] – maybe a Japanese interrogator spent a long time building a bond of trust with that Marine. But probably not. For one thing, time was short. I see people saying that building such a bond is in the long run more effective, but of course in war, time is often short.
You could consider the various agents that the Germans inserted into England: the British captured almost every one of them, and gave them the choice of cooperation (which included active participation in British deception schemes) or execution. Most cooperated.
The Germans tortured members of the various underground groups in Europe – and some of them never broke. But some did. You may have heard of Jean Moulin not breaking under torture, even unto death: but the Gestapo caught him because Jean Multon did break. To avoid being tortured, Multon agreed to work for the Gestapo. Over the next few days he led his captors to more than 100 members of the Resistance in Marseilles. He then gave away more in Lyons. Some of those he betrayed themselves broke under torture by the Gestapo. Things snowballed, and the whole network was torn to pieces.
People often argue that people under torture will say anything that their interrogators want to hear, and are thus useless as sources of information. There is something to that, but to a large degree that depends on what goals the interrogators actually have. For example, in the Iraq war, American higher-ups often didn’t want information – they wanted their fantasies confirmed. They knew that anti-American guerrillas couldn’t be motivated by nationalism or Islam – they had to be paid Baathist agents. Or there had to a connection between Saddam and Al-Qaeda. Whatever. Most told something close to the truth, but that wasn’t good enough, and so, torture. In much the same way, Stalin tortured until he got what he wanted – false confessions for show trials, rather than actual information about Trotskyist conspiracies (that didn’t even exist). Most people broke – I remember that a Chekist said, admiringly, that Lev Landau held out a long time – three broken ribs before giving in. The Japs at Midway wanted real info, not ammunition for their fantasies.
If an interrogator wants valid information, he can see if the stories of several different prisoners agree. He can see if their story checks with other sources of information. etc. It’s like any other kind of intelligence.
At least some of the arguments about the effectiveness of torture are obviously false, not even meant to make sense. For example, I have seen people argue that torture is pointless because the same information is always available by other means. Of course, since the products of various kinds of intelligence often overlap, you could use that argument to claim that any flavor of intelligence [ cryptanalysis, sigint, satellite recon, etc) is useless. But multiple leads build confidence. Sometimes, you can get information via torture available in no other way. If you are smart, and if information is what you really want.”