He did not extend the deferrment, he immediately declined his promise to enter the military after college.
How many deferments did Cheney get? Was it 5? He said he supported the war, but had other priorities. Bush's dad got him into the air guard, which kept him out of combat. The wait then was two years...bush enlisted the day he walked into the recruiter's office. I know because I got drafted and would have preferred the National Guard...
The repubs claim to be pro-military, Trump says he loves war...but they do prefer someone else do the dirty work.