For the stockholm convention 1972 pdf conference that took place in 1917, see Third Zimmerwald Conference. Sweden first suggested to the United Nations Economic and Social Council ECOSOC in 1968 the idea of having a UN conference to focus on human interactions with the environment.
ECOSOC passed resolution 1346 supporting the idea. General Assembly Resolution 2398 in 1969 decided to convene a conference in 1972 and mandated a set of reports from the UN secretary-general suggesting that the conference focus on “stimulating and providing guidelines for action by national government and international organizations” facing environmental issues.
The Soviet Union and other Warsaw Pact nations boycotted the conference due to the lack of inclusion of East Germany, which was not allowed to participate as it was not a full member of the UN. At the conference itself, divisions between developed and developing countries began to emerge.