According to the US "Defense Insights" website, Lockheed Martin delivered 300kW laser weapons to the US Department of Defense for demonstration of the US Army's "indirect fire protection capability high energy laser" project. This is the most powerful laser weapon successfully developed by the United States so far, marking the important progress made by the United States in directional energy technology. In 2016, the then head of the US Army Research and Technology Department said that the US Army was developing laser weapons. According to the plan, this weapon will be integrated into the "Indirect Fire Protection Capability - High Energy Laser" project in 2030. As a complementary weapon of conventional kinetic energy weapons, the US Army has vigorously promoted the research and development of high-energy lasers in recent years, and carried out several laser weapon technology demonstration and verification projects, including "laser mobile short-range air defense" and "indirect fire protection capability - high-energy lasers". The former mainly develops 50 kilowatt laser weapons to protect division and brigade combat teams from the threat of unmanned aerial vehicles, rotary wing aircraft and mortars; The latter developed 300 kilowatt laser weapons, mainly protecting fixed/semi fixed positions from the threat of unmanned aerial vehicles, rotary wing aircraft, fixed wing aircraft, mortars and cruise missiles. According to the statement of Lockheed Martin, on the basis of completing the technical breakthrough ahead of time, the company will carry out the demonstration of the project "Indirect Fire Protection Capability - High Energy Laser" at the end of 2022. The relevant person in charge of the project said that while improving the laser power and efficiency, the 300 kilowatt laser weapon reduced the weight and volume of the laser, thus reducing the difficulty of deployment. The US Army said that the 300 kilowatt laser weapon has a certain lethality to UAVs, rockets, artillery and mortars, which is helpful to improve air defense capabilities, and reduce system cycle costs by reducing logistics requirements. Laser weapons against low threat targets in the battlefield have the advantages of high accuracy, good adaptability to electromagnetic environment, strong concealment, and low use cost. Compared with conventional kinetic energy weapons, laser weapons also mean unlimited ammunition reserves and fewer warfighters, and are regarded as "an important force to change the form of war". Lockheed Martin said that its 300 kilowatt laser not only has the advantages of high efficiency, low loss, large radiation power, but also has high beam quality and high power density, which significantly improves the problems of large volume and poor reliability of laser weapons in the past. It can be installed on more platforms, providing an effective tool to combat low-cost threats. However, laser weapons still face many technical problems in the current development. First, the technology maturity needs to be improved, including improving the beam quality and control to the actual combat level. Second, there are many restrictions, such as air quality, power and cooling, which limit the range and beam quality of laser weapons, thus reducing their effectiveness. Third, the energy conversion efficiency of laser weapons is low. At present, the electro-optic conversion efficiency of the ideal optical fiber laser weapon is less than 35%. According to the calculation of the US military, the output power of the laser weapon that can intercept cruise missiles is at least 300 kilowatts. Laser weapons of this scale need to match huge energy supply devices, which restricts their mobility. Laser weapon