The traditional answer is that

传统的回答是
These guys actually did press up against the rows in front of them

他们实际上是在推挤前面几排友军
And that this provided a momentum

为其提供一种动力
That gave the front line an advantage in beating the enemy facing them.

使前线在与对面的敌人交战时具有优势
You can see all kinds of troubles.

同时也产生了一些麻烦
Why didn't the guys in the middle get crushed?

为什么中间的几排人没给压扁呢
I don't have any very good answers for that

我并没有令人满意的答案
and yet it is one part of the traditional explanation is this,

目前还有一种传统解释
and it's a very important one and much debated,

很重要同时也饱受争议
that at a critical time in the battle one technique

那就是在战局千钧一发的时刻
would be one side would give one great big shove.

有一项技术就是一方给对方致命一推
The word in Greek is othismos,

用希腊语来讲就是"othismos"