The Black Lives Matter movement hits a milestone on Thursday, marking 10 years since its 2013 founding in response to the acquittal of the man who fatally shot 17-year-old Trayvon Martin. Gunned down in a Florida gated community where his father lived in 2012, Martin was one of the earliest symbols of a movement that now wields influence in politics, law enforcement and broader conversations about racial progress in and outside the U.S. BLM activists and organizations plan to mark a decade of the movement with in-person and virtual events. Calls to action include a renewed push to defund police...