Dictionary entry

Redouble

Webster's Dictionary 1913

Re‐dou″ble (r?‐d?b″'l), v. t. [Pref. re- + double: cf. F. redoubler. Cf. Reduplicate.] To double again or repeatedly; to increase by continued or repeated additions; to augment greatly; to multiply.

So they

Doubly redoubled strokes upon the foe. Shak.