Meaning: an impenetrable defense; lit. copper wall, iron bastion
Original: 我们共护安全稳定,率先提出打击“三股势力”,坚决遏制毒品走私、网络犯罪、跨国有组织犯罪蔓延势头,联合举办反恐演习和边防行动,积极倡导政治解决国际和地区热点问题,构筑起守护地区和平安宁的铜墙铁壁。
Source: 习近平在上海合作组织成员国元首理事会第二十一次会议上的讲话
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