Hard data on decision making, and a better understanding of the way people think. The historical insights (including snapshots of how people lived and thought three or more generations ago) is a welcome bonus. So is gaining a better understanding of just what kind of people populate the border between civilization and hell. I'm young and I'd rather learn these lessons from third parties, life is, after all, rather short.

It's much harder to fudge the results of war than "management" - at the end of most large ones, the territory belongs to someone, and this is recognized by most authorities. So the data quality is better, provided you are careful about collecting it. If you are a manager, you can learn about leadership and how to do extraordinary things with ordinary people, or how to attract extraordinary people; if you are an employee, about which organisations and people to work for or avoid.

Is Jack Welch an extraordinary CEO, or was he, as is claimed in Thorndike's "The Outsiders", lucky to start his career with one of the largest economic booms known to man and retire right at the end of it? This impacts whether you'd like to adopt his methods: is stack ranking a great way to maintain high employee quality and engagement, or does it destroy corporate culture and lead to zombie companies with intense political in-fighting and little output?

On the other hand, nobody disputes today that a team of around 150 Selous Scouts and Rhodesian SAS, with no air support, wearing the enemy's uniforms and using the same weapons, literally walked into an enemy military base, killed thousands, and walked away without a SINGLE casualty (cf Operation Dingo); and when you dig, you realize this tiny group of men caused 3/4 of the enemy casualties in the entire war, many times in similarly one-sided operations, despite not existing before its start and not having any particular technological (the country was under embargo!), numerical or even political advantage. Such a group is worth studying no matter the politics.

It's also much easier to get several sides to the story: contrast Dick Marcinko's own controversial account of creating SEAL Team Six (which by the way has great insights on how to get things done in "big org") vs Robert Gormley who followed him at the helm of the group and had a more "official" view of the "Rogue Warrior". Or contrast Col. Charlie Beckwith's exceptional account of creating Delta Force, with a first hand, "from the ground" view by Eric Haney, and modern lessons on how it has evolved from Pete Blaber's excellent book about "helicopter" management (in this case literally).

You can learn about how a large organisation has managed to maintain efficiency and quality through centuries by picking up any of the numerous books on the US Marine Corps - Krulak's "First to Fight" and Chesty Puller's biographies were my starting point. Did you know Puller read 7 books about Korea on the ship that took him there? He is better known today for simply charging at the enemy in a straight line but like Patton who literally visualized great battles of the classical era to such details he could point at disappeared buildings, he was well read and thoughtful about how to best wage war.

What is it like to be "disrupted"? Read it first hand from Bloch's "Strange Defeat", describing just what it was like to face the new, fresh, efficient Wehrmacht when you are led by the last war's winners. Sir David Stirling's biography reads like a long list of impossible things - from breaking into an Army base to pitch his idea to a few generals, to being responsible for more aircraft losses with his handful of desert-dwelling infantrymen than the entire RAF in the sector. He failed a fair amount, too, including losing most of his men (!) on their first paradrop. And yet he got more budget and more men. Why?

You can learn a lot about human nature. Phoenix Program officers say that only 5-20% of a population holds firm views and will act on them; the rest will swing support to whoever controls the territory. How do you tell which is which, and can you turn the 5%? I've found this translates particularly well to analyzing which people you can count on (the famous "who'd be there when you're down"). It is interesting that most veterans will say you don't know who will keep a cool head and fire back until the bullets fly; there is little way of telling before then and no discernable pattern, so what does it imply about your interview process?

Finally, you can learn the limits of hindsight and analysis. Was COIN (the counterinsurgency doctrine advanced by the Pentagon since Vietnam) a success, as claimed by Chris Martin's analysis of open source documents about Delta Force in the 2000s? Or was it the reason American wars are so long and their results so controversial, as claimed by Col. Gian Gentile, because of a misinterpretation of previous successful COIN campaigns? (such as failing to notice that the British won in Malaya by displacing thousands of civilians from the affected areas, thus starving the guerilla)

I look at results that exceed expectations, try to draw some names out of it and then look up those names, preferably a first hand account, to understand how they thought and abstract the common traits. It is just amazing the extent to which the military can be a concentrated, more intense version of everyday life, perhaps because the stakes are so much higher.