Modern metropolises are teeming with police and national guards at the ready. They are well-equipped for dealing with riots, hostage situations, and the like. But they can't do much against people who wage asymmetric warfare. One person (or maybe a few people) were able to shut down London Gatwick Airport during the busy holiday season last year by flying drones near the runway. "The reports caused major disruption," says Wikipedia, "affecting approximately 140,000 passengers and 1,000 flights."

Now Jalopnik reports that someone is pulling the emergency brakes on subway cars, which is "destroying subway commutes."

This person has an established M.O., the source said, and Jalopnik confirmed this by reviewing internal incident reports. There are at least three so far. The suspect disrupts service primarily on the 2 and 5 lines from Flatbush Avenue in central Brooklyn to midtown Manhattan. He climbs aboard the rear of the train as it departs a station, unlocks the safety chains, somehow gets into the rear cab, and triggers the emergency brakes. Then, he disappears, most likely through the subway tunnels and out an emergency exit. Despite striking on average once a week for several months, the person has not been caught.

We suspect someone has intentionally disrupted thousands of commutes on the 2/3 lines today by activating multiple trains' emergency brakes. If you see any suspicious behavior, please @ or DM us details ASAP, including car #, so we can get trains back on schedule. — NYCT Subway (@NYCTSubway) May 21, 2019

Image: Allen.G/Shutterstock