The phrase "redoubled efforts" means to increase or intensify one's efforts or actions in order to achieve a goal or succeed in a task. Full definition
However, I do feel that we must now redouble our efforts in the league and can not afford any more slip ups. (justarsenal.com)
I applaud Sony for redoubling their efforts on their Reader Store. (goodereader.com)
Long an also - ran, particularly in the North American market, Samsung redoubled its efforts with a comprehensive line of touch, tablet, and Ultrabook systems. (digitaltrends.com)