Grammar: verb + 的 + verb What is the meaning of this form? 

Example:


  因为商纣王已失尽人心，军队也多不愿为他送命，于是逃的逃、降的降，起义的起义，朝歌很快就被攻克。纣王自杀，商朝就此灭亡。


I found many articles about simple reduplication of verbs in Chinese, like verb + verb or verb + 一 + verb (看看，看一看） but this one looks different (the way it's used).
I think  the structure {verb + 的 + verb} connotes that people do things without any constrains or scruple. It describes a disordered situation.

Compared to


  老师不在的时候，同学们玩的玩，闹的闹。// completely disordered there.


玩的玩 implied that if one wants to play, they just play (without any constrains or scruple).

In your sentence, 因为商纣王已失尽人心, therefore people just did whatever they thought right to them,  逃的逃、降的降，起义的起义(fled if one felt like flee, surrender if one felt like surrender, ...) The army was disordered or uncontrolled.

Stretch a bit: 逃的逃 -> 想逃的人逃了

P.S. the structure {verb + 的 + verb} is usually used to express a feeling and the feeling can be negative ones such as annoyed, sad, angry, etc or positive ones such as happy, joy, exciting, etc. 

Those examples above are negative. Here is a positive one: 


  操场上，同学们跳绳的跳绳，做操的做操，踢毽子的踢毽子，好开心啊！


Basically, the structure {verb + 的 + verb} is used to describe a situation and how you feel that situation. If you want to express a generic situation, you can just use other structure like 有的...有的, 有些...有些, etc.