Complex sentence: To the south the French offensive in Lorraine under General Nivelle was proving to be an unmitigated disaster and with losses in the neighbourhood of 200,000 men, it precipitated a wave of mutinies that paralyzed the French army for months.
Split into simpler sentences: To the south the French offensive in Lorraine under General Nivelle was proving to be an unmitigated disaster. With losses in the neighbourhood of 200,000 men, it precipitated a wave of mutinies that paralyzed the French army for months.