국교정상화가 · 국교정상화를
normalization of diplomatic relations
Example
한국과 일본의 국교정상화는 1965년에 이루어졌어요.
The normalization of diplomatic relations between Korea and Japan took place in 1965.
Word parts
국 nation+교 relations+정 proper+상 normal+화 become
Literally 'making relations between nations normal again'.