When Facebook was first expanding, they used a timeless military strategy to win their most-crucial first users. You can use this strategy to attack your toughest projects, by leveraging hidden complexity to lend devastating power to simple actions. Facebook faced tough competitors When Facebook was starting, in the mid-aughts, it was only available at colleges. It wasn’t easy to win new users on campuses that had their own social networks. Who wants to join the network nobody is on? That’s not where you find the big parties. That’s not how you spy on your crush. There was no point in promoting to students who already had better alternatives. Facebook would waste their limited resources, driving themselves out of business. There were plenty of competitors they needed to outlast. An established network at a college was a barrier to winning over any user at that college – a “defense,” if you will. Facebook needed to break through those barriers. The surround strategy: Attack from the flanks So they used what they called a “surround strategy”. Instead of directly trying to get users on a given campus, they got them indirectly. The strategy that decimated the Roman army 1800 years ago Facebook’s surround strategy was borrowed from the “pincer” military strategy. When you’re up against an opponent with strong defenses, it’s often not the best use of your resources to attack them head-on. It’s better to focus on the flanks. Hannibal used a pincer strategy in one of the greatest military upsets in history, at the Battle of Cannae, in 216 B.C., sending the Roman empire into a panic. As the Romans attacked from a concentrated center, the center of Hannibal’s forces fell back, creating a “crescent” shape that helped them attack the flanks. Eventually, Hannibal had the Romans surrounded. The Romans lost so many men that day, they had to lower the draft age to replenish their forces, and they reverted to using human sacrifices to try to please the gods. How Facebook won key users indirectly Facebook used this pincer strategy to indirectly win users at Baylor University, in Texas, which already had its own social network. Instead of promoting Facebook to users at Baylor, they focused on campuses near Baylor There weren’t already competing social networks at UT Arlington, a one and a half-hour drive to the north; Southwestern University, a one-hour drive to the southwest; and Texas A&M, a one and a half-hour drive to the southeast. To get the dirt on their exes, they needed to be on Facebook While Facebook wasn’t wasting resources trying to get Baylor students to switch social networks, those students started to hear about Facebook, anyway. The students in these surrounding colleges were former high-school classmates of the Baylor students. They were driving to one another’s campuses to bong beers and eat jello shots. They were hearing rumors their high-school sweethearts were getting naked with half the campus. They were laughing maniacally upon hearing the former bully was found passed out, naked with an armadillo. To get the dirt, to creep on one another’s profiles, or, sometimes to just stay in touch, they too needed Facebook accounts. So, without any promotion at Baylor, Facebook started winning users at Baylor. The birthday problem reveals the hidden complexity that make the surround strategy work This surround strategy works better than people expect it to. To understand why, think about the birthday problem, which I talked about on episode 237. How many people have to be in a room for a fifty-percent chance two of them have the same birthday? Most people guess 180 or 150, but the real answer: only twenty-three. The odds of shared birthdays climb rapidly as you add the first few dozen people to the room. Network effects between each person’s potential birthdates quickly add potential matches. Adding one person to a room of twenty people doesn’t add just one potential match, it adds twenty. Network effects...outside the network Facebo