What does the phrase "hi! Hi! hey!" signify in the Army song?

The phrase "hi! Hi! hey!" in the Army song serves as a rhythmic and spirited call to action. It captures the attention of soldiers and instills a sense of urgency and energy, prompting them to respond and engage. This call reflects the song's intent to rally troops, fostering teamwork and camaraderie through a shared, motivating chant. While other options may reflect elements of the song's overall spirit—such as cheering or motivating—this particular phrase is best understood as a direct encouragement for soldiers to come together and take action as a unified group. The emphasis is on immediate engagement, which is why the notion of a call to action resonates most closely with this phrase.