Language proficiency is a key prerequisite for interoperability within NATO armed forces, making foreign language education an essential component of professional military training. This paper examines learning motivation and learning effectiveness among Czech Armed Forces personnel attending English language courses aligned with NATO STANAG 6001. The research is based on a questionnaire survey of 320 learners conducted between 2023 and 2025, combined with their examination results. The study analyses differences in motivation and learning effectiveness with respect to proficiency level, gender, and age. The findings indicate that learning effectiveness is not directly dependent on course level, motivation structures are similar across genders, and the age significantly influences learning outcomes.