Multiple choice What was the obstacle that caused Alexanders army to turn back from conquering India? A huge river large mountain war elephants his men became ill Reveal answer Fill a bubble to check yourself C Correct answer Explanation At the Hydaspes River, Alexander's army faced formidable war elephants used by King Porus. The prospect of facing even larger armies with thousands of war elephants further east contributed to his soldiers' mutiny and refusal to advance.