It was not until near the very close of the medieval period that nations began to keep permanent diplomatic representatives at foreign courts. This custom is said to have originated with Louis XI of France. The practice at first met with great opposition, foreign ministers being looked upon as being in the nature of spies.

At first there was no regular system of rules either as to the classes of foreign representatives, their powers, or their relative ranks. Many bitter contests over questions of precedence took place at different European capitals.

To remedy this state of affairs the following protocol was adopted by the representatives of the various powers at the Congress of Vienna in 1815:

"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:

Division of Diplomatic Characters.

Art. 1. 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 Charges d'Affaires accredited to Ministers for foreign affairs.

Representative Character.

Art. 2. Ambassadors, Legates or Nuncios only shall have the representative character.

Special Missions.

Art. 3. Diplomatic characters charged with any special mission shall not, on that account, assume any superiority of rank.

Diplomatic Precedence.

Art. 4. Diplomatic characters shall rank in their respective classes according to the date of the official notification of their arrival.

Representatives of the Pope.

The present regulation shall not occasion any change respecting the representative of the Pope.

Form for Reception of Diplomatic Agents.

Art. 5. 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. 6. Ties of consanguinity or family alliance between courts confer no rank on their Diplomatic Agents. The same rule also applied to political alliances.

Alterations of Signatures in Acts or Treaties.

Art. 7. In Acts or Treaties between several powers that admit alternity, the order which is to be observed in the signatures of Ministers shall be decided by ballot."

This protocol worked badly in one respect, namely, that ministers of the second-class from small countries would often take precedence over ministers from large countries on account of a longer term of service. To remedy this defect, the following additional article was adopted at the Congress of Aix-la-Chapelle in 1818:

"Art. 8. It is agreed between the Five Courts that Ministers Resident accredited to them shall form, with respect to their precedence, an intermediate class between Ministers of the second-class and Charges d'Affaires."

After the adoption of this last article it became the custom for small countries to send ministers of the third class instead of the second.

The four grades of ministers are as follows:

1. Ambassadors, Legates and Nuncios.

2. Envoys, Ministers, or other persons accredited to sovereigns.

3. Ministers resident.

4. Charges d'Affaires.

The first three grades are accredited to the sovereign. The fourth grade, chargès d'affaires, is accredited to the minister of foreign affairs.

There is no rule as to what class of representative shall be sent from one country to another. This is left for each country to determine for itself; each country sends to another country, however, the same grade of representative which it receives from such country.