The convention establishing the Intergovernmental Maritime Consultative Organization (IMCO) came into effect on March 17, 1958. The convention, which had been drawn up at the United Nations Maritime Conference in Geneva in 1948, came into force when Japan ratified the convention, there by fulfilling the requirement that 21 states must become parties before the convention was to come into effect. A twelve member preparatory committee, which held two sessions in 1948, was to meet at UN headquarters during the spring of 1958 to prepare for the first session of the organization's assembly or legislative body.