Complex sentence: Carranza assigned a general to study the possibility of recapturing this territory from the U.S., but ultimately concluded that war to recapture territory from the U.S. was not feasible as aid from Germany could not be guaranteed due to the blockade by the Royal Navy.
Split into simpler sentences: Carranza assigned a general to study the possibility of recapturing this territory from the U.S., but ultimately concluded that war to recapture territory from the U.S. was not feasible. He believed that aid from Germany for such an effort could not be guaranteed due to the blockade by the British Royal Navy.