President Trump has sent federal agents and troops to Los Angeles and Washington, D.C., and he has vowed to send them to Chicago and other cities.

The president and his supporters see the influx of agents and soldiers as a means to curb crime and crack down on illegal immigration. Critics say Mr. Trump is using the deployments to punish Democratic-led cities and spread fear in immigrant communities. The move has prompted lawsuits, demonstrations and a scramble among local officials to respond.

Here’s how the federal presence on the streets has unfolded so far in some cities, and here’s how it may soon play out elsewhere.

Chicago

The Trump administration is making plans for escalated arrests of undocumented immigrants, using hundreds of federal agents who are being sent to the Chicago area. They are expected to use a naval base outside of the city as a staging area for operations. Local officials and immigrant advocacy groups are on high alert, reminding residents of their rights and urging caution.

Gov. JB Pritzker of Illinois said he believes the Trump administration is timing its crackdown to coincide with the city’s traditionally expansive Mexican Independence Day celebrations, which begin this weekend.