Appearing at Leeds Crown Court, Jeremy Green admitted murdering Nicole Waterhouse, 32, and attempting to murder Karen Browne, 24, at their flat in York.
The pair were stabbed, had their throats cut and were smothered by Green, 26, who took phones, bank cards and jewellery from them.
Peter Moulson QC, prosecuting, said Miss Waterhouse, known as Nicki, had 65 different injuries, including a damaged spine.
Mr Moulson said Green, who had been discharged from the Yorkshire Regiment for “minor dishonesty” earlier last year, had met both women at a dating night. Miss Browne had only been out with him a couple of times and was no longer seeing him.
Green went into the flat to burgle it on October 20, thinking the women had gone out after conning his way into the building, Mr Moulson said, but he decided to rob them when he found them in their bedrooms as he needed money for his rent the next day and a forthcoming trip to London.
The prosecutor said the attacks in the flat started with Green stabbing Miss Browne with the lock-knife and lasted nearly nine hours. Miss Browne, who survived, was rendered unable to move during the ordeal.
The court heard Green, who admitted murder and attempted murder, went to Afghanistan twice for acclimatisation but never left Camp Bastion and did not see active service. He told a psychiatrist he carried the lock-knife for protection following the murder of soldier Lee Rigby, in Woolwich, last year.
There were emotional scenes in court as Miss Waterhouse’s family faced Green, of Popes Head Court, York, one-by-one to read their victim impact statements.
Her sister Danielle said: “I will always have three sisters and no-one will take them away from me - not even him.
“He’s destroyed all our lives and he’s taken a part of our family we can never replace.”
She said: “My heart aches knowing she died alone with no-one around her.”
Miss Waterhouse’s father, John, said: “She was totally conned by this man’s evilness.”
Sentencing Green to 24 years in prison for the attempted murder of Miss Browne, to run concurrently with his life sentence for the murder of Miss Waterhouse, Judge Peter Collier QC said: “Your final savagery to each of them is almost beyond belief.
“Throughout the day you engaged in the most appalling and prolonged series of attacks on these young women.
“They were completely at your mercy. Apart from being physically stronger then them, you were armed throughout with a knife and you also armed yourself with other weapons - a belt, a bottle.
Mr Collier said: “It is impossible to imagine the torment to which they were both subjected and the terror they experienced over those long hours.”
The prosecutor said psychiatrists had examined Green but could find nothing to explain his actions and his flatmate said he was perfectly normal when he arrived at home following his violent actions.
Speaking outside court, Mr Waterhouse said: “Nicki was a sweet, kind girl who never did anyone any harm. She was loved without limits by our family and friends. What she endured that day, we will have to endure for the rest of our lives.”