已むに已まれず

やむにやまれず【止むに止まれず, 已むに已まれず】

〔衝動に駆られて〕 compulsively; on impulse; without being able to help [stop] oneself; unable to resist; 〔仕方なく; 追いつめられた気持ちで〕 against one's will; without having a choice (in the matter); having no choice; feeling compelled to….

●この惨状をなんとかして訴えるべく, やむにやまれず筆を執った. I felt compelled to write for your help in doing something about this terrible situation.