The 2006 “Day Without an Immigrant” mobilized millions and killed a draconian anti-immigrant bill. With ICE waging war on immigrant communities, the playbook for a mass strike already exists — we just have to study it.

Everyone looking to stop Immigration and Customs Enforcement (ICE) today has a lot to learn from the explosive mass movement that culminated in the “Day Without an Immigrant” on May 1, 2006. The spark was H.R. 4437, the Sensenbrenner bill, which passed the House of Representatives on December 16, 2005. Former representative Jim Sensenbrenner’s bill would have made it a felony for immigrants not to have papers, while also criminalizing acts of support and solidarity.

The threat was clear and the response spread fast. As one Los Angeles protest sign put it, “You’ve kicked a sleeping giant.” In the spring of 2006, between four and five million people marched in over 160 cities. And on May 1, over a million people walked out and poured into the streets across the country. Ports slowed; classrooms emptied; restaurants, shops, and job sites went short-staffed or dark. Chris Zamora, a marcher in Los Angeles, described what that collective power felt like on the ground: “It gives me chills to be a part of it. Thirty years from now, I’ll look back and say, ‘I was there.’”

The mass marches and economic disruption worked: Sensenbrenner’s bill was killed by the Senate in late May. It was a historic victory for the immigrant rights movement and the American working class.