For more than a year, hundreds of thousands of people of color have been terrorized by the Trump administration’s campaign of detentions, deportations, and violence. This reign of terror — centered on “surges” of heavily armed, masked agents carrying out aggressive arrests in urban centers, rather than the previous focus on detentions at the border and transfers from jails — led to a quadrupling of immigration arrests and a fivefold increase in deportations during the first year of Trump’s second term. The war on immigrants is taking place everywhere, but the administration had especially cruel treatment prepared for liberal sanctuary cities: first Los Angeles last summer; then the federal takeover in Washington, D.C.; then ICE surges in Chicago and Portland, Ore.; and finally Minnesota’s Twin Cities.

But these surges were met by a determined resistance that spread across the country and only grew more committed and better organized as ICE and Border Patrol violence escalated. Like the “whirlwind” moments described by the famed community organizer Saul Alinsky and his protégé Nicholas von Hoffman, the nationwide movement against ICE reached deeply into neighborhoods and diverse communities, moving tens of thousands of people into action — from heroic confrontations with federal agents and complex mutual-aid networks to massive demonstrations such as the Jan. 23 day of “no work, no school, no shopping” in Minnesota. A whirlwind moment “involves a dramatic public event or series of events that set off a flurry of activity,” write Mark and Paul Engler in This Is an Uprising: How Nonviolent Revolt Is Shaping the Twenty-First Century. “This activity quickly spreads beyond the institutional control of any one organization. It inspires a rash of decentralized action, drawing in people previously unconnected to established movement groups.”

In interviews with more than two dozen organizers in Minneapolis, St. Paul, Chicago, Washington, and Los Angeles, I learned about the structures that were built on the fly, as well as the existing relationships among diverse organizations that helped ground the resistance. Across the country, large numbers of people — some of them veterans of social movements, others newly activated — tackled longstanding questions about spontaneity and organization, silos and lanes, openness and security, and burnout and long-term organizing. Debates and disagreements that weren’t aired in the heat of the moment are now being taken up. And then there’s the million-dollar question: What’s next?