That battle is of great significance when viewed in the perceptive of the progress of the war
意思：这场战斗非常重要,当这场战役的细密的进程被看穿的时候.
1.be of great significance
be of 加名词,表示形容词意思.相当于,be significant(adj)
2.when 引导的是时间装语从句.viewed是非谓语动词,因为和主句的主语battle是被动的动宾关系（战役被人看穿,而不是战役看穿）,所以不用主动的viewing,而用viewed.
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