 What was Captain Walsh's main motive behind putting the narrator on the mission?
Perhaps there was method in Colonel Walsh's madness—murder-madness—when he ordered Major Polk to scan the planet for a guy named Joe. For example, he could have chosen a Second Looie for the job on Venus. We were somewhere in Area Two on Earth, takeoff point for any operations in Space II. The rest was gravy, and Colonel Walsh wasn't going to let me get by with gravy. "It will be a simple assignment, Major," he said to me, peering over his fingers. If Walsh really wanted to know the reasons for the revolt, I could give them to him in one word: Walsh. It had been going on for six months now and we'd lost at least a thousand men from Space II. It was just like Walsh to ship me off to a strange place. He'd goofed off on a pile of uranium that could've, and almost did, blow the barracks sky-high that night. And I thought about Colonel Leonard Walsh and how he was supposed to be quelling that revolt. Ever since Walsh had taken command, ever since he'd started pushing the natives around, there'd been trouble. "The guys back in Space II are searching high and low for you," I told him. "You've got the wrong number," he said, and I was a little surprised at his use of Terran idiom. My orders said I was to report to Captain Bransten immediately upon arrival.
 Walsh sought revenge against the narrator.
 Walsh sought revenge against the narrator.  Walsh wanted to test the narrator's intelligence.  Walsh wanted the narrator fired from his position.  Walsh wanted to test the narrator's competency.