Complex sentence: In 1933, she became a training ship and in July 1939, two months before the commencement of the Second World War, "Curacoa" was converted into an anti-aircraft cruiser.
Split into simpler sentences: In 1933, she became a training ship. In July 1939, two months before the commencement of the Second World War, "Curacoa" began a conversion into an anti-aircraft cruiser.