Challenges to national defence in contemporary geopolitical situation

English serves as the primary operational language of NATO, with proficiency assessed through the STANAG 6001 examination. This study analyses 240 authentic texts produced during the STANAG 6001 Level 2 writing examination at the University of Defence using corpus-based error analysis. Results indicate that failure to achieve Level 2 is mainly caused by systematic morphosyntactic errors and omission of obligatory language elements. Level 2 texts demonstrate greater grammatical accuracy and complexity, with implications for targeted English language instruction in military higher education.