You shouldn't have this problem if you 1) hire for intelligence, drive, cooperation, and passion about the mission or opportunity, 2) give them continual opport

You shouldn't have this problem if you 1) hire for intelligence, drive, cooperation, and passion about the mission or opportunity, 2) give them continual opportunities to grow and take on increasing responsibility, and 3) compensate them appropriately (as a manager, privately reevalute title and comp every three months for the first year). Of course, these are the same things (among others) that are true for every engineer. There's an endless supply of juniors to choose from, so there's no excuse for a bad hire. If they leave for more money that you could have paid them, that's on you, too. Do those things and you'll win their loyalty.