A man was left with a bloody nose and a broken wrist after an internet date went wrong.
Jordan Swift met his victim via the Snapchat messaging service.
Their first face-to-face meeting went well, but Swift turned to violence during a subsequent meeting.
Swift could give no explanation for his behaviour, Teesside Crown Court heard.
"The victim is a 34-year-old male," said Emma Atkinson, prosecuting.
"He was contacted by the defendant who requested a meeting.
"The victim collected Swift and went back to his flat where there was some intimate contact.
"After this Swift's mood changed, he became quiet, then angry, and without warning punched the victim to his face, causing his nose to bleed.
"The victim says the incident is a blur, but he also suffered a broken wrist which required surgery and a plate."
The court heard the victim is still upset by what happened.
"He says he is on edge with people," said Ms Atkinson.
"For some time he was unable to leave the house, he suffers from panic attacks and has trouble sleeping,"
Swift, 20, of Bright Street, Hartlepool, admitted causing grievous bodily harm on June 28.
He was of previous good character.
Stephen Constantine, defending, said in mitigation: "Mr Swift has a troubled background, but despite that he had maintained an exemplary character.
"He doesn't drink to excess or take drugs, and was in the Royal Navy until he was medically discharged.
"There is some confusion in his life, he has little recollection of that evening but maintains he only struck a single blow.
"Mr Swift has obtained a job working away as a cable puller for which he can earn £500 a week, or more with overtime.
"He is genuinely remorseful, and there has been no hint of a repeat of this behaviour."
Judge Howard Crowson sentenced Swift to 15 months in prison, suspended for one year, 20 rehabilitation activity days, and ordered him to pay £1,000 compensation.
The judge told him: "The meeting was initially friendly, it may be that what took place came to be regretted by you.
"It has been said there is some confusion in your life which is a good way to put it.
"You have had problems in the past which some defendants would seek to use as an excuse.
"I accept your remorse is genuine, and I think it unlikely you will offend again.
"Sentencing guidelines say a sentence can be suspended if there is a realistic prospect of rehabilitation."