I think 為之 in English is simply " is"
為之 is composed of 為( is) and 之( particle - emphasize "is" )
五人[為之]一伍 (five soldiers [is] one unit)
二十五人[為之]一排( twenty five soldiers [is] a platoon)
** in brief description like this, you can omit the particle 之 and just write
五人[為]一伍 ,
二十五人[為]一排
點先至[為之] 成功？= what [ is ]success?
** it is a complete sentence
1. the verb 為 has one syllable, it sound unnaturally brief in a sentence,
2. 為 has more than one meanings. Therefore, 為之 shouldn't be simplified here.
** In 「援兵到達，各人精神為之一振」 ( reinforcement soldiers have arrived, everyone's spirit is uplifted for that)
「為之」 is 「為」 ( for) + 「之」 ( that)
為之 is composed of 為( is) and 之( particle - emphasize "is" )
五人[為之]一伍 (five soldiers [is] one unit)
二十五人[為之]一排( twenty five soldiers [is] a platoon)
** in brief description like this, you can omit the particle 之 and just write
五人[為]一伍 ,
二十五人[為]一排
點先至[為之] 成功？= what [ is ]success?
** it is a complete sentence
1. the verb 為 has one syllable, it sound unnaturally brief in a sentence,
2. 為 has more than one meanings. Therefore, 為之 shouldn't be simplified here.
** In 「援兵到達，各人精神為之一振」 ( reinforcement soldiers have arrived, everyone's spirit is uplifted for that)
「為之」 is 「為」 ( for) + 「之」 ( that)