中世纪城堡经常遭受长时间的围困。

Medieval castles often endured long ___sieges by enemy forces.

环保组织对这家污染企业发起了长达数月的法律攻势。

The environmental group conducted months-long legal ___siege against the polluting company.

在持续数月的舆论压力下，这位政治家最终宣布辞职。

After months of public ___protests, the politician finally announced his resignation.