Isaacs had previously admitted aggravated burglary, causing grievous bodily harm and seven counts of fraud. He will spend 16 years in custody and four on licence, the judge ruled.
During sentencing, Judge David Ticehurst said Mr Booth was an "extraordinarily remarkable gentleman" whom Isaacs "savagely attacked with a claw hammer which you took with you for that purpose".He said: "It was a brutal and utterly senseless attack on him."
Judge Ticehurst also said Isaacs met the criteria for the extended sentence as he showed an "apparent lack of remorse or concern" for attacking Mr Booth for a "paltry" amount of money.
The court heard Isaacs, formerly from Exeter, went to Mr Booth's home on 22 November intending to obtain money as he had not eaten for days and was "starving".He initially offered to carry out repairs to the roof, but when he was turned down he repeatedly hit the 96-year-old with a hammer and left him for dead. h Isaacs denied carrying out the attack when he was arrested Isaacs used Mr Booth's bank card to buy food at a McDonald's fast-food restaurant in Bridgwater after the attack.
The court heard Mr Booth was hit six times on the head, as well as on the arms with the claw side of the tool. Between each blow Isaacs shouted "money, money, money".Mr Booth suffered a number of skull fractures, bleeds to the brain, deep wounds to both his arms and a fracture to his right hand.
Speaking after he had recovered, he said he was told one of his arm injuries showed he had hit back at his attacker."I'm saying I blame myself because I was special services and I think I really should have known how to deal with this, but I didn't."I was too old, obviously," said Mr Booth
.In a statement released after the sentencing, the veteran's family said: "On 22 November last year, a light was shone on the very best and worst of humankind, when our father was subjected to a brutal and cowardly attack inside his home."Miraculously, though left for dead, and against all odds, he survived."In the very difficult six months since, our father has shown extraordinary courage and determination as he's battled with the pain and long-term effects of the injuries."He is truly inspirational."
Det Ch Insp James Riccio, from Avon and Somerset Police, said: "It was a cowardly act and it's a miracle Mr Booth survived these horrific injuries"
Mr Booth, who joined the Royal Navy at 18, took part in one of the most secret operations of the D-Day invasion in Normandy in 1944, and
talked about it in a 2013 BBC documentary.He was part of a team of submariners who submerged close to Sword Beach.On the day of the landings he and his colleagues left their craft in a fold-up canoe to shine beacons to guide the Allied landing craft safely to shore.