Complex sentence: During 1942 and into the next year, there were many technical and administrative problems Then in September 1943, a decision was made to use the British and American systems in liberating Europe; thus, the large REL order was never filled.
Split into simpler sentences: During 1942 and into the next year, there were many technical and administrative problems. In September 1943, a decision was made to use the British and American systems in liberating Europe; thus, the large REL order was never filled.