the word "stiffen"
The ISF (Iraqi Security Forces) are stiffening, that they’re capable of defending Baghdad, that they would be challenged to go on the offense, mostly logistically challenged,” said Dempsey.
What does "stiffening" mean in this sentence? How to use it?

Question

the word "stiffen"
The ISF (Iraqi Security Forces) are stiffening, that they’re capable of defending Baghdad, that they would be challenged to go on the offense, mostly logistically challenged,” said Dempsey.
 What does "stiffening" mean in this sentence? How to use it?

Answer

Stiffening in this sentence means that the ISF are growing stronger.
Stiffen is basically something that is hard, so when a group "stiffens" it means it can't be broken etc.