This song describes the situation and status of the war so far, from a number of perspectives on a number of factors.
"George, attack the British forces" - This was written in a letter by Congress, which was read by Hamilton. Congress no longer trusts Washington, but they also don't fully know the situation on the frontlines, which is where the ignorant and over-generalized line "George, attack the British forces" comes from.
"The cavalry's not coming" - There is no more backup coming and the Revolutionary army is already short on men.
"Don't engage, strike by night" - British soldiers were better trained, had better equipment, and numbered far more than the Revolutionary army. Washington knew they could never beat any British army in a front out battle, so they resorted to using smart tactics.
"I ask for French aid, I pray that France has sent a ship" - Lafayette called to France for help and the deciding factor of the American Revolutionary War was France's decision to help.
"We write essays against slavery" - Laurens and Hamilton are both early abolitionists, and this is when Laurens began organizing his idea for an African American battalion in the Revolutionary army.
"And ev'ry day/Sir, entrust me with a command" - Hamilton desperately wants to fight, but Washington instead chooses Charles Lee, who is not a very good general. During the Battle of Monmouth, Lee retreated when they were supposed to attack, resulting in Washington transferring Lee's command to Lafayette.
Painting of the Battle of Monmouth
This infuriated Lee and he started cussing Washington out to everyone. While Washington is unaffected, Hamilton becomes enraged by this, and wants to challenge Lee to a duel but was directly ordered by Washington not to. As a result, Laurens volunteers to duel Lee.