"The system worked. I've always been proud of my Army," he said. "All I want to do now is go north and hug my kids and my wife."
The case unfolded with the Pentagon under heavy pressure to confront what it has called an epidemic of rape and other sexual misconduct in the ranks.
As part of the plea deal, Sinclair's sentence could not exceed terms in a sealed agreement between defense lawyers and military attorneys. The agreement, unsealed Thursday, called for Sinclair to serve no more than 18 months in jail, but the judge's punishment was much lighter.
Prosecutors did not immediately comment. Capt. Cassie L. Fowler, the military lawyer assigned to represent the accuser's interests, had a grim expression after the sentence was imposed and declined to comment.
In closing arguments, prosecutors argued Sinclair should be thrown out of the Army and lose his military benefits, while the defense said that would harm his innocent wife and children the most. The two sides also offered contrasting arguments about the seriousness of the misdeeds that felled the general.
"It's not just one mistake. Not just one lapse in judgment. It was repeated," said prosecutor Maj. Rebecca DiMuro. "They are not mistakes. We are not in the court of criminal mistakes. These are crimes."
The defense had called a host of character witnesses this week to laud Sinclair as a selfless leader in hopes of getting a lenient punishment.
Defense attorney Richard Scheff said Sinclair will retire from the military.
"He has new mountains to climb," he said.
Scheff said the case against Sinclair was one of pure adultery, which is a crime in the military.
"People ought to be encouraged to come forward and the right cases brought. This was not the right case," Scheff said.
Prosecutors did not ask the judge to send Sinclair to jail, even though the maximum penalty he faced on the charges to which he pleaded guilty was more than 20 years.
The judge could have also dismissed Sinclair from the Army, which would have likely wiped out his Veterans Administration health care and military retirement benefits.
The general also pleaded guilty to adultery and using his government-issued credit card to pay for trips to see his mistress and other conduct unbecoming an officer.
Sinclair had been accused of twice forcing the female captain to perform oral sex during their affair.