Wow, I see that you are a junior in high school and reading Founding Brothers that is terrific.
By the early 1790's it was clear to Washington that Britain had no intention of living up to the agreements in the Treaty of Paris 1783. Britain had not removed all of its troops, they basically ignored its financial responsibilities to American merchants, and were increasingly impressing Americans on the high seas. There is no doubt that these kinds aggressions to any sovereign nation would be a justified call for war. The book suggests that Washington understood just how vulnerable the United States was at that time and knew the U.S. could not withstand another war so soon after the revolution. Therefore, if he could begin a dialogue with Britain instead of using force it might keep the peace. Washington sent John Jay to Britain to try and settle the difficulties diplomatically. Although Jay made several concessions to the British despite their aggressions towards the U.S. his mission improved relations with Britain decreasing the threat of war, thus promoting foreign diplomatic policy relations with a foreign nation.