They were armed, but not very dangerous.With pillows at the ready, some still in their pyjamas, they marched into battle. An hour later it was all over.
There were no winners and no losers, just scores of happy faces.
The city's fourth annual Pillow Fight Day was held on Saturday, attracting several hundred people to Chater Garden in Central in the biggest turnout yet.
Tom Grundy, 31, a local blogger who organised the event, said: "It's a nonsensical, noncommercial, non-political expression of community love in an annual feathery fury of global unity.”
Watch: Feathers floating up, hundreds join Hong Kong pillow fight
"There are over 100 cities participating today, beating each other with soft objects.
"I noticed it wasn't happening in Hong Kong and not possible in China so I contacted the international pillow fight people.
"Hong Kong is unique in that people dress up in funny costumes," said Grundy.
It was the second time the event was held in Chater Garden, after two years at the smaller Statue Square.
Jacopo Ograbek, 23, a student at the Chinese University of Hong Kong said: "It's great for Hong Kong to have events like this to get people out to have fun. It's also good for IKEA. I see a lot of people got pillows there for 20 bucks."
Frankie Ying, 26, a designer, said: "I had a tough week. Pillow fighting is a great stress reliever. And it's such a nice day today to be outside."
University student Peggy Leung, 18, added: "My friends and I saw the event on Facebook and decided to come. I didn't get to pillow fight when I was a kid."