The original US Navy Polaris had not been designed to penetrate ABM defences .
The Royal Navy had to ensure that Polaris ' small Polaris force operating alone , and often with only one submarine on deterrent patrol , could penetrate the ABM screen around Moscow .
The original US Navy Polaris had not been designed to penetrate ABM defences , but the Royal Navy had to ensure that its small Polaris force operating alone , and often with only one submarine on deterrent patrol , could penetrate the ABM screen around Moscow .