Is Peace Corps a form of National Service (similar to the military)?
Short Answer: No.
Since 2006 Peace Corps is no longer a form of national service.
From DoD FOIA:
"...We have consulted with the Office of Military Accessions Policy, Office of the Under Secretary of Defense for Personnel and Readiness in order to respond to your request. That Office advises that the initial law that authorized the National Call to Service (NCS) Program (enacted under section 531 ofthe FY02 National Defense Authorization Act) did allow service in the Peace Corps and/or AmeriCorps to simultaneously count as military service after completion of the required active duty and time in the Selected Reserve."
" However the National Defense Authorization Act for 2006 (PL 109-163) removed the Peace Corps from eligibility and left only AmeriCorps as an alternative National Service Program. Additionally, that Office knows of no other program that would allow the Peace Corps to count as military service."
- Department of Defense: FOIA DoD_case_number_07-F-1259