请教白勇语法全解的一道题

光杆杆

刚开始看白勇语法全解就遇上不明白的了，麻烦哪位高手指点一下下吧！多谢了！直接上题了：

Where once the union had acquiesced to the prejudices of its English-speaking members by supporting the imposition of an alien tax on immigrant workers,after 1897 the United Mine Workers made a determined effort to enlist Italians and Slavs in its ranks.

划线部分就是正确答案，不太明白解释中写的Where是做（尽管）从句，Where 在这里引导的不是主语从句吗？怎么会做为（尽管）解释呢？

不明白呀，不明白！！

casforain

Where once the union had acquiesced to the prejudices of its English-speaking members by supporting the
imposition of an alien tax on immigrant workers,  [after 1897状语]  ［the United
Mine Workers主语］ ［made谓语］ ［a determined effort宾语］ ［to enlist Italians and Slavs in
its ranks宾补］.

光杆杆

明白了，但是where引导的划线部分是做的什么成分呢？

casforain

你在第一楼不是写得很清楚了吗。。。寒。。。

光杆杆

不好意思，你没明白我的意思，我是不太明白下面答案解释中为什么Where会有“尽管”这个意思~~~~嘿嘿，俺太笨了，麻烦你再指点下下吧！！狂谢了！！~~~~