If you are disabled from a combat-related injury, and are waiving your military retired pay for VA pay, you can get both now, without having 20 years in! I just heard about this as it recently passed. Here is a link:

http://www.donhq.navy.mil/corb/crscb/crscmainpage.htm
https://www.hrc.army.mil/site/crsc/index.html