From Longman Dictionary of Contemporary Englishredoublere‧doub‧le /riːˈdʌbəl/ verb → redouble your efforts→ See Verb table
Examples from the Corpus
redouble• Ashenden doubted it, his doubt redoubling as the coach drew further and further away from Oxford along the A34.• The company is redoubling efforts to make its young advertising salesforce more professional.• When the United States intervened, the Front redoubled its efforts.• From then on the pretty servant girls eyed him with a lustrous regret and redoubled their attentions.• Instead of rethinking their programme, they redoubled their efforts to implement it.• You will to the utmost maintain a middle attitude and redouble your efforts to carry out our policy. 