Complex sentence: In 1985, France withdrew from membership in IBI and by the end of 1986 also Spain withdrew and the crisis of the IBI was initiated leading to the dissolution of this organisation in 1969.
Split into simpler sentences: In 1985, France withdrew its membership from IBI and by the end of 1986 Spain also withdrew. This was the start of a crisis within the IBI which led to the dissolution of this organisation in 1969.