I need help with two terms.

Italian Guy

Milforum Hitman
Hi guys, I really need to know the difference between preemption and prevention.
It's for Strategic Studies Exam ( next week ). When I have a doubt I know who to turn to for help 8)
thanks guys.
pre-empt - if you pre-emt an action, you prevent it from happening by doing something wich makes it unnecessary or impossible strategic plans which demanded pre-emtption as the only method of averting defeat

prevent - to prevent something means to ensure it does not happen thismethods prevent pregnancy

This is from a dictionary and as I understand it an action can be pre-emptive to prevent something ( Bush made a pre-emptive attack on Iraq in order to prevent the use of Iraqi WMD :p )