On 14 February 2017, the Facebook group "MediaTakeout" published a video that purportedly showed federal troops in an armored tank patrolling areas of Chicago at President Donald Trump's behest:
SHOCK IMAGES: Donald Trump Just Sent FEDERAL TROOPS Into The CHICAGO GHETTO . . . There Are ARMED TANKS . . . Rolling Through CHIRAQ!!! #Trump #Chiraq #MarshallLaw
Within a few days of its initial posting, the MediaTakeout video was viewed more than two million times, but it does not show federal troops. Instead, this appears to be a SWAT vehicle called a Lenco BearCat that is owned and operated by the city of Chicago.
In fact, the words "Chicago Police" can clearly be glimpsed on the side of the vehicle as it passes by the camera at around the 15 second mark:

While we have not been able to track down the exact date this video was published, Chicago started using the BearCat long before Trump became president. The city has been using similar armored vehicles since at least 2010. DNAInfo posted a photograph of one of these vehicles being used during a "barricade situation" on 9 February 2017:

While President Trump has talked about imposing martial law in Chicago, he has not sent federal troops or armored vehicles into the city as of February 2017. The video shows a BearCat owned and operated by the Chicago Police Department carrying members of the city's SWAT team, not federal troops.