<p>The process of nuclear fusion in the presence of a laser field was theoretically analyzed. The analysis is applicable to most fusion reactions and different types of currently available intense lasers, from X-ray free-electron lasers to solid-state near-infrared lasers. Laser fields were shown to enhance the fusion yields, and the mechanism of this enhancement was explained. Low-frequency lasers are more efficient in enhancing fusion than high-frequency lasers. The calculation results show enhancements of fusion yields by orders of magnitude with currently available intense low-frequency laser fields. The temperature requirement for controlled nuclear fusion may be reduced with the aid of intense laser fields.</p>