The friendship between the two countries has a long history.
Tips
history
From Bai Juyi's Tang-era epitaph 《海州刺史裴君夫人李氏墓志铭》: 「夫源远者流长，根深者枝茂」 — deep sources make long rivers; deep roots make lush branches. The water metaphor is literal.
usage
Formal praise. Default phrase when describing the length of a tradition, culture, friendship, or institution. Almost always positive.
