Complex sentence: Reconstruction followed quickly; by the end of 1945, the polder was declared drained again and the rebuilding of roads and bridges, houses and farms, was greatly facilitated by the experience of building them the first time.
Split into simpler sentences: Reconstruction followed quickly; by the end of 1945, the polder was declared drained again. Rebuilding of roads and bridges, houses and farms, was greatly facilitated by the experience of building them the first time.