The man chased his partner out of their Rotherham home when she escaped with their eight-week-old son at 3am, on June 27, said prosecutor Susan Evans.
As she put the baby into a car and tried to get in, he grabbed her, threw her to the floor and punched her numerous times in the face.
The defendant, who cannot be named for legal reasons, took the baby and evaded the police helicopter by hiding, before police officers found them both unharmed in his back garden, at 5am.
He initially refused to hand the baby over and officers talked with him for an hour before he suddenly agreed, said Ms Evans.
His partner of two years was left with bruising and cuts to her nose and mouth.
The court heard he has previous convictions for criminal damage and assault occasioning actual bodily harm.
The defendant watched via video-link from HMP Leicester as his partner told the court under oath she wanted to end their relationship. However, no restraining order was imposed.
Francis Edusei, mitigating, said: "They had all been drinking at home that night.
"At the conclusion of the festivities he made a joke that didn't go down terribly well and his partner became upset."
He said his client was diagnosed with post-traumatic stress disorder in 2016, as a result of combat experience in Afghanistan, but had since sought treatment.
In the two and half weeks he has spent in custody he has carried out work, Mr Edusei said, adding: “He has realised that he needs help and is going to avail himself of the help that is available.”
He pleaded guilty to assault occasioning actual bodily harm and being drunk in charge of a child.
Judge Michael Slater sentenced him to six months, suspended for two years, and ordered him to attend 30 rehabilitation days and complete the building better relationships course.
“This is a last chance for you and I very much hope that you are willing to take it,” the judge said.