As for most languages, the french language practice obeys some rules. One of these rules is called *"règle de l'article contracté"*. It states that when  *"une préposition"* is followed by *"un article défini"*, the result should be "un article contracté" (contracted article).

In the case of:

> une compression **du** personnel

*"du"* is here the contracted article of *"de le"* which respectively are *"préposition + article défini"*. Consequently, it is incorrect to say:

 > **une compression de le personnel**

The use of *"de"* / *"du"* depends on whether personnel is definite or not. In our case, it isn't so one must use *"du"*.

If *"personnel"* is definite, *"de"* should be used as in:

> une compression **de** personnel de la comptabilité.

Note that *"de la"* of *"de la comptabilité"* is not concerned by the rule in question since it is *"du genre féminin"* (feminine gender).