Themes
There's nothing stronger than the heart of a volunteer.
— Lt. Col. Jimmy Doolittle ‧ Pearl Harbor

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The volunteer’s willingness is given greater weight than any other kind of strength. Heart stands for commitment or courage rather than physical power. The statement praises choosing to take part, suggesting that freely offered effort has a force that cannot be measured by capability alone.
Context reviewed