Complex sentence: As commander of this division, he participated in the Battle of France of 1940, but he came to be seen as a weak leader when the lightly defended French town of Le Quesnoy was able to resist his armoured forces for some four days.
Split into simpler sentences: As commander of this division, he participated in the 1940 Battle of France. He came to be seen as a weak leader when the lightly defended French town of Le Quesnoy repulsed his soldiers and tanks over four days.