The following treaties explicitly specify at least a limited requirement for mutual assistance between the respective Contracting Powers:
South Asian Trade, Scientific Undertaking and Military Agreement (SATSUMA):
Japan, India, Philippines, China, Formosa, Chosen, Persia, Pacifica
Franco-Atlantean-Russian Treaty of Mutual Assistance (FAR)
Russia, Atlantis, France
North American Regional Cooperative (NARC)
United States, Canada, Mexico
South Africa - India Naval Treaty (SAINT)
South Africa, India
Danish-Siamese Mutual Defence Treaty
Denmark, Siam
Esquel Treaty
Argentina, Chile
Polish-Romainian-Yugoslavian Friendship (?) Agreement (PRYFA)
Poland, Romania, Yugoslavia
The following alliances exist but treaty text is either unavailable or secret:
UK-Iberia-Italy-Denmark
United Kingdom, Iberia, Italy, Denmark
Alianza del Atlantico Norte y Mediteraneo (AANM)
Iberia, Italy, Netherlands, Denmark
South Africa - Netherlands Trade Agreement (SANTA)
South Africa, Netherlands
Danish-Dutch Alliance
Netherlands, Denmark
The Commonwealth
United Kingdom, Canada, Australia
UK-Greece
United Kingdom, Greece
SAE-Nordmark
South Africa, Nordmark