せざる ない
sezaru enai

i-Adjective
Expression

1. cannot avoid doing; cannot help but (do); is compelled to do; (feel) obliged to (do); has to do

かれ書類 しょるい署名 しょめいせざるを なかった。
karewa shoruini shomē sezaruo enakatta.
He was forced to sign the document.