During the New Guinea campaign MacAuthur sent an infantry regiment (sorry, don't have the number and division right off 35th ID?) across the Owen Stanley mountian range on what was marked as a trail on his maps to outflank the Japanese at Buna. The regiment set off on this march finding the trail didn't exist. Over the next month and half they fought their way through jungle over a 12,000 ft + mountian range losing nearly 2/3rds of the regiment to disease and deprivation.
Worse, when the survivors arrived at Buna they found the rest of the division had been flown in weeks before and were already occupying the area they were supposed to take. That ranks in my book as one of the most idiotic operations of the war.