倒装So sudden (was the attack) that the ememy had no time.为什么不可以用 did the attack so提前不是要部分倒装吗?was 提前了不是完全倒装了?

是部分倒啊，was就是倒啦，如果全倒，你后面的that从句也要倒了

So sudden (was the attack)
是
The attack was so sudden
的倒装。
既然我们不说 The attack did so sudden，那么倒装就不是 so sudden did the attack 。

我为你比较一下,这样你会清楚一些.
1 The attack was so sudden that the ememy had no time.
主句的动词是was,在变成倒装句时不能写成------did -- - be.所以只能是was提前：
So sudden WAS the attack that the ememy had no time.
2 The attack CAME so suddenly that the ememy had no time.
主句的动词是came,在变成倒装句时必须写成------did- -- -come,就成了半倒装(==助动词+真正动词)：
So suddenly did the attack come that the ememy had no time.
现在,你明白了吗?