Army Secretary John McHugh announced Friday that he was stripping a general officer two ranks before retiring him after he was chareged with sexual assault and other misconduct.
"This is the first time the Army has reduced a retiring general officer by two ranks in a decade," said an Army statement.
As part of a plea deal, Sinclair pleaded guilty to adultery, maltreatment of a subordinate, engaging in improper relationships, willful disobedience of an order, wrongful use of a government travel card, wrongful possession of pornography, and conduct unbecoming an officer.
He was fined $20,000 and issued a reprimand.
Groups supporting victims of military sexual assault and some lawmakers had decried that outcome as too lenient, and called for Sinclair to face jail time or to be dismissed from the Army without pension pay.
McHugh noted that he is prevented by federal law from taking further action, saying he did what was "legally sustainable."
"Sinclair displayed a pattern of inappropriate and at times illegal behavior both while serving as a Brigadier General and a Colonel. I therefore decided there was sufficient evidence and cause to deny him those benefits," Hugh said in the statement.
The high profile case has been an embarrassment to the Army at a time when several lawmakers have made prevention of sexual assault in the military a top priority.
McHugh's decision to demote Sinclair to a lieutenant colonel would lower, but not take away, his retirement pension.
"During Capitol Hill hearings, I was asked whether Sinclair would receive a pension after proceedings were complete," McHugh said.
"Under federal law, if a person has earned a pension because of their years of service, they are entitled to those benefits; Congress might consider a change in the law that would allow greater flexibility and accountability," he said.