Gettysburg address的一句话讲解谢谢!

Gettysburg address的一句话讲解谢谢!
It is for us,the living rather,to be here dedicated to the great work remaining before us—that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion—that we here highly resolve that these dead shall not have died in vain—that this nation,under God,shall have a new birth of freedom—and that government of the people,by the people,for the people,shall not perish from the earth.这句话的语法结构?我完成一头雾水啊谢谢!

这段话有5个版本,下面这个版本是公认的,林肯的原话（网上可以听到这段话录音）是这样的：It is for us the living,rather,to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced.It is rather for us to be here dedicated to the great task remaining before us—that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion—that we here highly resolve that these dead shall not have died in vain—that this nation,under God,shall have a new birth of freedom—and that government of the people,by the people,for the people,shall not perish from the earth.
两个句子主干是it is for us to be dedicated to .这里的rather不用翻译,只是表示对比上文所说意思上的转折.然后第一句的iving修饰us,就是活着的我们；which从句修饰unifinished work,什么样的未完工作.应当是我们这些活着的人在这里为那些牺牲的人已取得巨大进展但仍未完成的崇高事业奋斗.
第二句It is rather for us to be here dedicated to the great task remaining before us应当是我们在这里为面前依然存在的艰巨任务奋斗.然后后面跟了4个并列的that 从句来说明这个任务是什么.第一个that从句from these honored dead we take increased devotion to that cause（我们会继承先烈的目标更加努力）,然后这个从句里还有个从句for which they gave the last full measure of devotion来修饰cause（为了这个目标他们竭尽全力奋斗都最后一刻）.第二个that 从句里that we here highly resolve 后面又跟了个状语从句that these dead shall not have died in vain修饰前面的动词resolve（我们誓言牺牲的人不会白白牺牲）.第三个that 从句that this nation,under God,shall have a new birth of freedom（在天主之下的这个国家将获得新生）.第四个that 从句and that government of the people,by the people,for the people,shall not perish from the earth （民有、民治、民享不会从地球消失）.
再问： that从句是什么从句？
在主句里作什么成分？
谢谢！！！
再答： 同位语从句，用来进一步说明前面某个名词的具体内容，相当于名词，与前面的名词同位。在这段话里，几个that 从句成分与“task ”同位。