"There is a green hill far away,
Without a city wall,
Where the dear Lord was crucified,
Who died to save us all."
I notice from Googling this just now that the references have all replaced the original word 'without' with 'outside' (which was the intended meaning) . So, obviously I wasn't the only one...
Anyway, what Eisenhower was questioning was how far you can go before you destroy internally ('from within') what you are trying to protect from external forces ('from without').