A gang of four tried to kill a 78-year-old man in a knife attack in central London, Scotland Yard said.
The victim, reported to be Indian Lieutenant General Kuldeep Singh Brar, was left with serious injuries in Old Quebec Street near Marble Arch.
Police were initially called to reports of an assault around 10.40pm, but said they are treating the attack as attempted murder.
Scotland Yard said the victim, who was visiting London, was with his wife when four men attacked him and slashed his neck.
He was taken to hospital but has now been discharged, the force said.
Detectives want to speak to the people who stopped to help him, and said they are keeping an open mind about any motive for the attack.
Mr Brar was involved in a military operation against Sikhs in Armritsar in 1984 that left an estimated 1,000 people dead.
The attackers were all wearing dark clothes and had long beards, and ran away towards Oxford Street.