As soon as Zhang landed in Nanjing, Chiang had him placed under arrest by military police.{{sfn|Shai|2012|p=98}} Zhang wrote Chiang aan obsequious letter of apology. Although he never disavowed his role in the Xi'an incident, he admitted that what he had done was a crime, and asked to be punished. He intended the letter to be a private assurance of loyalty to Chiang, but the latter had the letter published so as to discredit Zhang.{{sfn|Shai|2012|pp=99-100}} [[Li Liejun]] then presided over a show trial which convicted Zhang of abducting the Generalissimo and attempting to change government policy, sentencing him to ten years in prison.{{sfn|Shai|2012|p=101}} Chiang had him pardoned just a few days later, on 4 January 1937, but with the stipulation that he not be given his civil rights back and that he would remain under protective detention.{{sfn|Shai|2012|p=102}}
