Performance of high energy laser (HEL) directly determines the damage ability and strike range of laser directional energy, and the United States has launched a series of plans to develop high-power, high-efficiency, compact, lightweight and robust lasers for battlefield. In 2019, the high energy laser scaling initiative (HELSI) was proposed, and the latest national laser amplification route was formulated. Firstly, the background, research contents and implementation stages of this HELSI were introduced. Secondly, the research progress of 300 kW in the first stage of HELSI was analyzed. Finally, the subsequent influences of HELSI progress was reviewed. Comprehensive analyses show that the Lockheed has won the first stage by its spectrally combined fiber laser technology, not only obtaining production orders of 300 kW HEL of US Army, but also entering the second stage of HELSI to get development contract of 500 kW HEL firstly. The progress of HELSI has made missile defense agency (MDA) pay more attention to laser weapons used to intercept boost-phase ballistic missiles. HELSI supports four technical approaches of HEL for competitive development. However, which one will eventually be deployed on the battlefield in the future needs to be strengthened the early research and break through the technical fog.