The barbarization of Roman army had a long history and was a gradual and lasting process, so the pace of barbarization of army steeping up was an inevitable product.
Later the correspondent spoke into the bottom of the boat. "Billie!" There was a slow and gradual disentanglement. "Billie, will you spell me?" "Sure," said the oiler.
The historical development of a language is hardly a sudden transformation of one language into another, but a gradual and constant process, often indiscernible to speakers of the same generation.