Complex sentence: As the nutritional value of official civilian rations remained below subsistence level, the French continued to evade all control efforts and depended on the illegal market for their survival: countermanding food restrictions became something of a national pastime.
Split into simpler sentences: As the nutritional value of official civilian rations remained below subsistence level, the French continued to evade all control efforts and depended on the illegal market for their survival. Thus countermanding food restrictions became something of a national pastime.