Looks like Cheney had an aversion to the draft during the Vietnam war.
http://www.cbc.ca/fifth/dickcheney/ascent.html
1965
NOVEMBER 1: Cheney gets his fourth draft deferment.
Cheney graduates and is once more listed as 1-A, ready for military service.
1966
JANUARY 19: When his wife was about 10 weeks pregnant, Cheney applies for 3-A status, the ''hardship'' exemption, which excludes men with children or dependent parents. It is granted.
1967
JANUARY: Cheney turns 26 and is no longer eligible for the draft.