In the face of crises on every side, the nation must unite.
Tips
history
From 《管子·戒》: '君外舍而不鼎馈,非有内忧,必有外患' — 'when a ruler lodges abroad without feasts, if it is not inner trouble it must be outer danger'. The Warring States text 《管子》 coined the pairing.
register
Formal, common in history writing, political commentary, and business analysis. The two halves 内忧 + 外患 can appear separately (e.g. '没有内忧,却有外患').