This pattern expresses that someone is compelled to do something or something happens to them against their will, usually because of external forces like rules, disasters, or other people's decisions. It is a passive construction based on the verb 余儀なくする (to force), so the subject is the one who is forced. The nuance is that there is no choice; it's not about personal preference but about unavoidable circumstances.

Use it when you want to emphasize that the action was not chosen freely. It often appears in news reports, formal writing, or serious conversations about events like cancellations, resignations, or changes. Because it's a stiff, literary expression, it sounds odd in casual chat. For example, if a concert is cancelled due to a typhoon, you'd say 中止を余儀なくされた, not やむを得ず中止した (though that's also possible, this pattern highlights the external pressure).

When the action is a noun like 延期 (postponement), 撤退 (withdrawal), or 変更 (change), use を余儀なくされる. When the action is a verb, you need to nominalize it with こと, as in 辞めることを余儀なくされる. The passive form される indicates that the subject receives the forcing, so the subject is the one who has to undergo the action.