Conceived in ~1971 [1,2] and first experimentally demonstrated in 1994 , quantum cascade lasers have become the most importance sources of infrared laser radiation in the 3.5 μm to >12 μm spectral region. With needs already identified at even longer wavelengths, QCLs are being pursued vigorously as sources of terahertz laser radiation. The mid wave infrared (MWIR) and the long wave infrared (LWIR) regions are, however, significantly more important because of a number defense, homeland security and commercial applications critically require the capabilities of QCLs. These capabilities include size, weight and power considerations (SWaP), which make QCLs unique among all other potential sources of laser radiation in this region including optical parametric oscillators, optically pumped semiconductors and optically pumped solids. In this presentation, I will summarize some of the key advances and status of QCL technology as well as defense and civilian applications of the MWIR and LWIR quantum cascade lasers.