Complex sentence: Lyautey returned to his former position in Morocco at the end of May and immediately decided on a new strategy, concentrating his forces in the Moulouya Valley, convinced that the submission of the tribes in this area would lead to the collapse of the Zaian resistance.
Split into simpler sentences: Lyautey returned to his former position in Morocco at the end of May and immediately decided on a new strategy. He concentrated his forces in the Moulouya Valley, convinced that the submission of the tribes in this area would lead to the collapse of the Zaian resistance.