A car was rammed into a wall by two other vehicles before its driver was attacked in Bishopbriggs.
The incident happened on Balmore Road in Cadder at 10pm on Monday.
The black Ford Focus was forced off the road by two other vehicles near Luddon Training Centre before the driver was attacked.
The 52-year-old man was taken to Glasgow Royal Infirmary.
The male passenger in the car, aged 50, left the scene to ask for help.
Forensic officers are inspecting the vehicle.
Detective inspector Allan MacInnes said: “The motive for this incident is unknown. It’s vital we establish the exact circumstances of what took place and why.
“I am appealing to motorists who were in the vicinity around the time of the incident to contact us.
“Although, you may not have seen the actual incident you may have seen cars driving at speed along Balmore Road and I would appeal to you to contact us with any information you may have.”
It is not known how many occupants were within the other two vehicles.
Anyone who was in the vicinity of the accident, particular those with any dash cam footage are asked to help.
Anyone with information is asked to contact 101.