In the USMC, the phrase “What makes the grass grow?” is a call‑and‑response used in training and motivation. The traditional Marine answer is “Blood, blood, blood!”

Meaning

• The line is part of Marine Corps cadence and culture, symbolizing sacrifice, combat, and the blood shed by Marines on the battlefield.

• It reinforces the idea that progress and victory are paid for by hard work, suffering, and, in war, lives given in service.

Cultural context

• Drill instructors use it to fire up recruits, build aggression, and connect them to generations of Marines who have fought before them.

• Some Marines also connect it literally to the nutrients in blood (like nitrogen and phosphorus) that can help plants grow, which becomes a darkly humorous “science lesson” behind the slogan.