Final answer:
Exact details about the year Congress authorized voluntary retirement for enlisted Soldiers after 30 years of service are not provided in the text, but the evolution of veteran benefits over time suggests that military pensions and retirement plans likely developed progressively after significant legislation such as the GI Bill in 1944.
Step-by-step explanation:
The historical context of Congress authorizing retirement benefits for soldiers suggests the focus is on legislation that provided for military pensions. While the provided text does not directly answer the question regarding the authorization of a specific year for voluntary retirement for enlisted Soldiers after 30 years of service, historical records show that the concept of military retirements evolved over time, particularly in the post-Civil War period. Detailed legislation records would be required to pinpoint the exact year. However, the Servicemen's Readjustment Act of 1944, also known as the GI Bill, was significant for veterans' benefits post World War II, suggesting a progressive movement to provide such benefits.
Without specific reference to the exact year Congress authorized a retirement plan providing three-quarters of pay and allowances after 30 years of service, we can infer that this structure likely evolved as social support for veterans increased throughout the 20th century, following the precedent set by earlier legislation and benefits such as pensions and the GI Bill.