This report builds on work in the project "Assessment of ground combat efficiency at the operational level" during 2017 to 2019. It is a continuation of a report from 2019. The need for empirical data for validating combat models is explained. During the 1990s, FOA developed a method for operational level field testing of the armed forces. Lessons identified from that work are deemed valuable for re-establishing the ability to methodically test the combat effectiveness of units and unit types. Thereby, better data for validating combat models could also be acquired. Combat models require different levels of validation depending on their purpose, this is briefly examined. The most important conclusions drawn from the period 2017- 2019 are presented.