Fiber laser technology has the potential to make a significant impact in many defense applications, from LIDAR and remote sensing to high energy laser weapons systems, in addition to numerous industrial, medical and scientific applications. This revolutionary new laser technology offers many intrinsic advantages over traditional DPSSLs and has received considerable support from key funding agencies over the last 10 years, including DARPA and the Joint Technology office (JTO) amongst others. With the aid of this funding several groups have now demonstrated small, compact and lightweight single mode fiber devices operating at the 1-10kW power level. There are research and development programs in the Air Force, Navy and Army currently. Funding to demonstrate beam combining of fiber lasers to the 25kW level is in place with programs such as RELI and Excalibur. More recently, the BAA call from the Office of Naval Research specifically calls for the development of high energy laser weapon technology suitable for ship board defense to be demonstrated on platform by 2016 and fiber technology is one possible solution being considered. Active deployment in the next decade is anticipated by some branches of the military. Widespread publications in the research community have demonstrated an impressive array of power scaling fiber laser results, both CW and pulsed at wavelengths from 1um to the eyesafe 1.5um and 2um wavelengths. Advantages associated with fiber technology are not only high wallplug efficiency leading to reduced electrical power requirements and easier system cooling, but also robustness, good beam quality, compactness and highly flexible system performance. These, coupled with (remote) fiber delivery options make the technology unique in many applications. This tutorial will cover the major aspects of designing and building a fiber laser, from the fiber itself through the various state of the art fiber components, and discussing the system parameter space that best makes use of the intrinsic advantages of the technology. Applications from industrial material processing though to defense and homeland security will be reviewed.