Put yourself in his position. For three weeks, the States' Men had control of the debate with only a short speech from James Wilson of Pennsylvania to support the Constitution.
Meanwhile, a Pennsylvania jurist's son has fired an artillery barrage and has hit some targets. An anonymous writer from New York has dissected the document like a surgeon and exposed significant flaws. A learned and respected jurist from New York has torn Hamilton a new one. An anonymous lawyer from Massachusetts has played the prosecutor and -- come Thursday -- will issue a detailed bill of indictment against Hamilton's project.
Hamilton needed to get the debate back into his court, and the only way to do this was to hit back first and lay out his course of action as superior.
It's interesting to note that the next four Federalist Papers were about foreign affairs and were written by his fellow New York lawyer, John Jay. They will come up next week and the week after.