Complex sentence: When the 54th's issue of rifles arrives, and Forbes is assigned to train the men in marksmanship, instead of training the men in the correct manner, Forbes allows the men to shoot at bottles for target practice.
Split into simpler sentences: When the 54th's issue of rifles arrives, and Forbes is assigned to train the men in marksmanship. Instead of training the men in the correct manner, Forbes allows the men to shoot at bottles for target practice.