military pension
A pension paid to former military personnel or their survivors. This is a specific legal and administrative term in Japan.
He receives a military pension.
恩給 is a general term for a pension, especially one granted by the government. 軍人恩給 specifies a pension for military personnel.
Compound of 軍人 (military person) and 恩給 (pension). The term is a straightforward combination of its components.