- It is a mutual defence pact that was invented by France in 1928 at the Paris confrence and was then joined by the UK in 1928.6. after it had ratifyed the treaty.
| Nation. | Year of joining. | Year of leaving. |
|---|---|---|
| France | 1928 | - |
| UK | 1928.6 | - |
| Portugal | 1939. | |
| Belgian | 1940 | |
| Greece | 1941 | |
| Yugoslavia | 1946 | |
| Netheralnds | " | |
| Greece | 1956.6 | |