那位年迈的学者花了十五年时间，将几个世纪的军事史浓缩成了一本简洁的手册。
The aging scholar spent fifteen years distilling centuries of military history into a single concise handbook.
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解释
提炼、浓缩（抽象内容）
The aging scholar spent fifteen years distilling centuries of military history into a single concise handbook.
提炼、浓缩（抽象内容）