As best I can remember, I was sitting on my couch one evening after work and decided to watch “World War Z.” It had been out for a few years, but I had mostly avoided it because I felt like it came out around a time where everyone was going crazy for anything zombie related. Especially in video games, I feel like that era had like 9 different survival zombie games, all of which I played and promptly got bored of. In World War Z, there is a scene where Brad Pitt is told a story about Israel’s history and how a bunch of analysts unanimously agreed that Arab troop movements weren’t a threat, just a month before the Yom Kippur War. As the story goes, this led them to make a change to their processes. If nine of us look at the same information and arrive at the exact same conclusion, it is the duty of the tenth man to disagree. No matter how improbable it may seem, the tenth man has to start digging with the assumption that the other nine are wrong. Something about this story, whether the origins are true are not, really resonated with me. I was doing work at the time on a red team for a multinational tech company, and the idea of this “tenth man rule” felt familiar to what we sought to do at a company level. But I thought we could take it further. I thought we should take it further. Why should a red team exist purely to challenge the assumptions of the broader business, and not challenge their own assumptions? It wasn’t long before we were practicing this rule in our team meetings and on our team engagements. It served as a valuable reminder, every time, that we needed to stay cognizant of our own assumptions and our own biases. To have a reliable Devil’s Advocate voice in each meeting, even if that voice changed every meeting, even if that voice changed multiple times throughout the meeting, it reminded us that we, too, are subject to the assumptions that we enjoyed seeking out so much in the systems around us. It’s been many years since this story took place, I’ve since left that job, took another red team job, left that job, and now work as a security engineer for a much smaller company. To this day, I carry the tenth man rule with me into all my meetings, though I will admit that it is much harder to act on in a lean company where everyone is focused on moving quickly. But it is for that same reason that the rule is as important to me as it ever was. Be the contrarian. Be the Devil’s Advocate. Be the Red Team. Be the Tenth Man.