London's police force is putting more armed officers on the streets — a visible response to attacks by Islamic State-inspired groups in Europe.

Metropolitan Police chief Bernard Hogan-Howe said Wednesday he's increasing the number and the visibility of the officers "to protect the public from all manner of threats."

The training of the officers was announced earlier this year and their deployment came after Hogan-Howe warned recently an attack in Britain was a case of "when, not if."

Londoners are proud that most police do not carry guns, and the fundamental principle remains unchanged. Even with the changes, most of London's 31,000 police officers will not be armed.

But the recent attacks underscore the challenge police face in responding to a situation in which they are outgunned.