What key factor contributed to the reluctance of the Congress in the late 19th century to support military expansion?

The reluctance of Congress in the late 19th century to support military expansion can be attributed significantly to the lack of foreign aggression at that time. The period following the Civil War was marked by a relative absence of external threats to the United States. This lack of perceived danger led many lawmakers to view military expansion as unnecessary and potentially wasteful. Without pressing security concerns, Congress was less inclined to allocate resources to increase military capabilities or to support initiatives that would expand the military's size and influence.

The context of the era also included a focus on domestic issues, reflecting the needs and concerns of the American population who prioritized reconstruction and economic growth over overseas military ventures. As such, the environment during this time created a sentiment that a strong military presence was not critical, resulting in hesitance from Congress to endorse any substantial military expansion efforts.