manhattan 语法 verb tense 【求助】！！

manhattan sentence correction 第 119页，verb tense部分，第三个例句上面一点：

Also note that the later past eventdoes not need to be expressed with a Simple Past tense verb. You could just use a date or another time reference.
Right: By 1945, the United States HAD BEEN at war for several years.

Using....The 1^st clause expresses an early action in Simple Past. Then, a second clause expresses a latter action in Past Perfect to indicate continued effect(by a still later past time).
Right: The band U2 WAS just one of many new groups on the rock music scene in the early 1980’s, but less than ten years later, U2 HAD fully ECLIPSED its early rivals in the pantheon of popular music.

这两句讲解的话偶看不懂嘤嘤。。。还有那个later past tense 也不理解。。。
还有后面为何要用过去完成时HAD fully ECLIPSED ？
偶真是智商捉急！！！


谢谢谢谢！！！
附上偶搞的08prep语法笔记PDF版以示感激！
http://forum.chasedream.com/GMAT_SC/thread-690078-1-1.html

by 1945（1945 is a past time ，by 1945 is some time earlier than 1945 for example ，1943-1945）


less than ten years later （ten years is a past time， less than suggests some time prior to ten years ，past of past）

第一句懂啦！

第二句，less than 10 years later不是发生在1980之后了吗？并且可以用一般过去时的，为什么必须要用过去完成时呢/
谢谢！！

nope，they are two separate statement，with the former has nothing to do with the latter（that‘s the tricky point）


former clause：causal statement about the band（simple past is used）


latter clause：second description，（less than ten years later）


the clause set up two time frame 1. ten years later 2. less than


so you should use past perfect （you cannot use the tense of former  to deduce that of the latter；they are not related）

umm

ten years later 是一个simple past
less than 建立起了和这个simple past 的联系，早于这个ten year laters


假设时间为1940 ，ten years later 为1950，less than ten years later是1949，here u got the past perfect