What about Iraq? He served beyond his 20 years of service and decided to resign from the national guard on May 16, 2005 to focus on his congressional run. There was no indication that his retirement was blocked. His unit went out in March 2006.
I guess this depends on perspective; I think at this point he was 41, ready for politics, and had served for 24 years. Bad timing but nothing malicious.
A lot of the right wing takes I see portray Walz as hopping back on the helicopter in the middle of battle and heading home.