intervene|intervened|intervening

联合国被要求介入边境争端。

The UN was asked to ___intervene in the border dispute.

哈里斯介入以阻止袭击。

Harris ___intervened to stop the attack.

一些人反对介入内战，担心冲突会延长。

Some argued against ___intervening in the civil war, fearing prolonged conflict.