Because he wanted to escape his unhappy and unfortunate past as Dick Whitman. He was in the Army when he and the real Don Draper came under fire, etc. See season one for more details.

Thank you. I'll catch Season 1 for more details

You're trying to understand THIS show without first watching the first season?

I wouldn't know where to begin.

I'd suggest newer viewers wanting a better understanding get the Season One DVD. And even then that's no guarantee you will understand a character's motivations!

This show keeps my interest and challenges me because of it's ambiguity. So much of TV is predictable--this show is not and that's why I enjoy it.

Switching dog tags with the dead Don Draper also gave Dick Whitman a quick exit from Korea and I wonder if that was part of his motive or just an added benefit. We've never seen why DW joined the army in the first place. Switching identities with Don Draper may have offered him an escape from something more terrible than growing up with the stigma of whore child.

I just want to slap you

just kidding

I used to think he just wanted to escape his crumby family but now I think he saw a way out of the war as well. Maybe he grabbed the real Don's dogtags at first to save for his family, but when he woke up in the hospital and they thought he was Don Draper, the idea sort of set in.

Anyway, It sure would be hard to do this today! I know a few people who "went underground" in the
late 1960's and they have not had such a great life, to put it mildly. Don was also very fortunate to have Anna turn out to be so cooperative and actually an accomplice. They seem so much in tune, I wonder why there were no romantic sparks there? Is her bad leg or legs part of that plot?

It sounds like Anna and Dick both benefitted from the stolen identity. It sounds like the real Don Draper was a womanizer by the way he never mentioned he had a wife to Dick Whitman. I sensed that Anna almost felt a sigh of relief that the real Don Draper was dead. By Anna giving away the real Don Draper's identity was her last act of defiance. You go, Anna! Cheers ;o)

because he could.