Gettysburg Address 语法分析

that引起the great task的同位语从句.与马丁路德金的I have a dream里的用法类似，只是这里中间有了个小间隔(remaining before us)，就引起了点理解的小麻烦。
（from these honored dead ）we take increased devotion to that cause （for which they gave the last full measure of devotion;）
括号外的是主句，for which是