During the years 1648 to 1815 the relations of states became more complex, and the business of international negotiation more delicate. Diplomatic practice, always tending to look to precedent, suffered severe strains under the ambitious monarchs occupying the thrones of Europe after the Peace of Westphalia. Principles and precedent were often disregarded to obtain political ends. So great was the friction that at length some of the more commonly disputed questions were settled at the Congress of Vienna, 1815.
(_b_) The question of relative =rank= of state agents gave rise, in the days before the Congress of Vienna, to many difficulties. The protocol of that Congress of March 9, 1815, together with the eighth article adopted at the Congress of Aix-la-Chapelle, Nov. 21, 1818, give the basis of present practice as follows:--
"In order to prevent in future the inconveniences which have frequently occurred, and which may still occur, from the claims of Precedence among the different Diplomatic characters, the Plenipotentiaries of the Powers who signed the Treaty of Paris have agreed on the following Articles, and think it their duty to invite those of other Crowned Heads to adopt the same regulations:--
+Art.+ I. Diplomatic characters are divided into Three classes: That of Ambassadors, Legates, or Nuncios.
That of Envoys, Ministers, or other persons accredited to Sovereigns.
That of Chargés d'Affaires accredited to Ministers for foreign affairs.
+Art.+ II. Ambassadors, Legates, or Nuncios only shall have the Representative character.
+Art.+ III. Diplomatic characters charged with any special Mission shall not, on that account, assume any superiority of Rank.
+Art.+ IV. Diplomatic characters shall rank in their respective classes according to the date of the official notification of their arrival.
The present Regulation shall not occasion any change respecting the Representative of the Pope.
+Form for Reception of Diplomatic Agents+
+Art.+ V. There shall be a regular form adopted by each State for the reception of Diplomatic Characters of every Class.
+Diplomatic Agents of Courts Allied by Family or Other Ties+
+Art.+ VI. Ties of consanguinity or family alliance between Courts confer no Rank on their Diplomatic Agents. The same rule also applies to political alliances.