On April 18, Hong Kong police arrested 15 well-known pro-democracy leaders for their roles in allegedly organizing and participating in unlawful mass assemblies last August and October. While thousands of protesters have been arrested since the start of Hong Kong’s pro-extradition protests last June, the coordinated round-up of relatively moderate opposition politicians came as a surprise to many.

These 15 opposition figures represent a broad swathe of the city’s pro-democracy movement, ranging from veteran politicians to youthful activists. Many of the arrested figures have been longtime stalwarts of the city’s pro-democracy movement dating back to the 1980s, and many had previously served on its Legislative Council.

Unlike the younger generation of localist, pro-independence activists, these politicians have tended to represent a more moderate tendency within the wider pro-democracy camp that is open to dialogue with the Chinese government and accepts China’s ultimate sovereignty over the city. For them, the role of the pro-democracy camp is to hold China to the promises and commitments outlined in the Basic Law and the Sino-British Joint Declaration, and to secure the implementation of “One Country, Two Systems” in both name and fact.

Far from being at the forefront of the latest wave of protests, or even the Umbrella Movement in 2014, many of these figures have been the target of trenchant criticism by younger, more radical activists who embrace a more explicitly pro-independence agenda and have little time for establishment tactics.

To put it more simply, the barrister and ex-legislators arrested on Saturday have long stood for working within the system, using Hong Kong’s courts and legislature to advance their agenda; the younger activists who have taken the lead in the latest wave of protests are more inclined to storm the Legislative Council and question the independence of the city’s judiciary.

So who are these people, exactly? Let’s take a closer look.