In the mean time events in North America continued to agitate the diplomatic world of Europe and to stir up trouble. As Great Britain had begun to interfere with the commerce and navigation of France, the relations between the two countries grew daily more strained. France had come to an understanding with Spain, that by the beginning of the year 1778, the two powers would have to combine to make war on Britain, but Carlos III., getting old and more and more conservative, did not want to depart from his policy of neutrality and wanted to end his days in peace. When on the thirteenth of March, the British secretary of state received from the French ambassador a note, saying that France and the United States of North America had signed a treaty of friendship and commerce without any definite advantage to France, but that the king was determined to protect the lawful commerce of his subjects, a state of war was established between the two kingdoms. Efforts to change the decision of Spain were repeated; the return of Florida to Spain was offered with the consent of the United States. But Florida had by this time lost all charm for the conservative court of Spain, so awed by the fact that a republic was to be the neighbor of her American possessions that it was bound not to do anything that might help the insurgents, and sooner or later kindle the desire for independence in their own colonies. Only the prospect of recovering Gibraltar might at that moment have swayed the decision of Spain. But that seemed beyond reasonable possibility.