New York Governor Kathy Hochul is deploying 750 soldiers from the state's National Guard to help police check commuters' bags in the busiest stations on the city's subway system.
Another 250 officers from New York State Police and state-controlled Metropolitan Transportation Authority Police will also join the effort, which Ms Hochul said is intended to deter crime.
She announced the deployment in response to recent high-profile assaults on commuters and transit workers.
Crimes on the subway were down about 15% in February compared to the same month in 2023, according to police data.
Ms Hochul, a Democrat, said that commuters were not reassured by "rattling off" crime statistics.
"Saying things are getting better doesn't make you feel better," she said, "especially when you've just heard about someone being stabbed in the throat or thrown onto the subway tracks. There's a psychological impact."
Soldiers of the New York National Guard, a military force jointly controlled by federal and state leaders, do not have arrest powers in peacetime, but will help police officers who do.
New York City Mayor Eric Adams, a Democrat who used to patrol the subway when he was a police officer, said he sent about 1,000 additional city police officers into the subway in February after a rise in January in assaults and thefts.
He has emphasised that crime remains rare on one of the world's largest subway networks, with about six incidents a day, mostly thefts, on a service that sees more than four million daily trips.
Mr Adams is reintroducing bag checks, an occasional practice used by the New York Police Department in which officers set up a table near subway turnstiles and pick out commuters for searches.
Riders Alliance, a New York commuter advocacy group, said that Ms Hochul's deployment of the National Guard would have the opposite psychological impact than intended.
"While well-intentioned, deploying troops to the subway is more likely to increase the perception of crime among people who don't ride public transit than to protect the millions of people on platforms and trains," accoding to Danny Pearlstein, a spokesperson for the alliance.
There were 38 robberies and 70 thefts, including pick-pocketing, on the subway system in February, compared to 40 robberies and 98 thefts in the same month last year, police data shows.
There were 35 assaults, the same number as for February 2023. About 90 million trips were taken on the subway over the month.
In her announcement, Ms Hochul cited an attack last week on a subway train conductor who was slashed in the neck by an unknown assailant while he leaned his head out of a train window.
It was one of several assaults on subway workers in recent weeks, to the anger of their union, leading to service disruptions as Metropolitan Transportation Authority (MTA) employees stopped work to file safety complaints.
Ms Hochul said the MTA would install new security cameras in conductor cabins, adding that she was asking the state legislature to pass a law allowing judges to ban people who assault workers and commuters from the subway system.
In another incident, six people were shot at a subway station in the Bronx last month.
