The night action by the Japanese against the Marines' positions on the sandbar at the mouth of Alligator Creek is known as the Battle of the Tenaru. The Japanese had badly underestimated the scale of the US forces on the island. This led to overconfidence on their part, and so in the early hours of 21 August 1942, 917 Japanese attacked entrenched and well-defended Marine positions on the Tenaru sandbar. They lost over 780 dead in that single battle.
The quote Leckie recites, "Without a sign, his sword the brave man draws, and asks no omen, but his country's cause.", while he and his fellow Marines eat before landing on Guadalcanal, is from the ancient Greek poet Homer.
During the battle of Tenaru, you can clearly see the blank rounds in the belt magazine in a close-up shot of the machine gun team.