President Trump promised an “overwhelming presence” of federal agents and military troops on the streets of Washington when announcing a crime crackdown earlier this week.

Four days in, however, National Guard soldiers have mostly been seen massing in parking lots and taking photos with tourists. Federal agents have made a larger show of force, mainly through traffic checkpoints and immigration-related arrests.

National Guard soldiers were seen Thursday morning at Union Station, the transit hub near the Capitol, where the sight of armed security is not uncommon. But the impression of a major military presence across the city has yet to materialize.

Officials have telegraphed a larger surge over the next few days, saying that 100 to 200 soldiers might be on the streets at any given time to support police officers. The troops cannot make arrests themselves.

The situation resembled President Trump’s deployment of some 4,000 California National Guard soldiers and 700 Marines to Los Angeles in June during protests against the Trump administration’s immigration crackdown.

Troops ringed federal buildings in downtown Los Angeles during protests and provided some backup on immigration raids. But others spent much of their deployment in a sprawling tent city, where they were based, or sitting in trucks with little to do, eroding morale.

In Washington on Wednesday night, the most visible sign of President Trump’s takeover of the local Police Department was a sobriety checkpoint operated by local and federal police agencies on a busy street near downtown, which drew a crowd of jeering protesters.

Officers from other federal law enforcement agencies, including the F.B.I. and U.S. Border Patrol, also assisted in traffic stops and other police operations overnight, sometimes rolling through intersections in large unmarked vehicles.

The F.B.I. director, Kash Patel, said that the bureau and “our partners” — a potentially long list of both federal and local agencies — had made 45 arrests overnight, 29 of which were related to immigration matters.

The Metropolitan Police Department makes an average of 68 arrests a day in Washington, a city of roughly 700,000 people.

Perhaps the highest-profile arrest during the federal crackdown involved a man charged with assaulting a federal officer earlier in the week by throwing a sandwich at him.

The man tried to turn himself in on Wednesday night to face the assault charge, his lawyer said, but was arrested instead.