He bought a promotion to lieutenant in January 1799, but became bored with the lack of action and sold this position in the autumn of 1800.
He spent three more years there, mainly in Germany, renewing his connections with influential people and learning about the political situation.
The Prime Minister Spencer Perceval read this work, interviewed Johnson and gave him a position in the Foreign Office as a confidential agent.
[4] After the Treaty of Paris was signed in 1814, bringing temporary peace, Johnson was appointed chargé d'affaires at Brussels, and then was made British consul at Genoa.
He was said to be "in close and friendly correspondence with the principal ministers and generals and leading public characters of almost all the states of Europe".