To retrieve his son in the future, and then personally educate him, making him realize the facts and change his statement, saying he was captured by accident while wounded in battle, but with his resilience and unyielding spirit, he was eventually rescued by the Special Forces.
Sending Little Curtis to the military was originally meant as a means to gild his resume, serving as a Congressman is definitely a boon with a service record.
Ralph thought this was not a serious blow to the family's honor but rather a great opportunity to shape his son into a war hero.
As long as his son returns and acts out the script he'd designed, and he contacts his friends in the media to hype it up, getting on television and such, Little Curtis' political future would be boundless, possibly even surpassing his own.
The Pentagon initially strongly opposed this unthinkable plan.