On the Shu side of the Battle of Wu Zhang Plains, do not allow Wei Yan do be slain. (Target 2) If he says a message about withdrawing to a base to recover, that does not mean he's been forced to retreat and you can still get the achievement. To complete this, I follow him to the lowlands near the river and take bases/kill officers near him, which should also complete targets 2 and 3. Like most of the escort targets, this one can be completed most easily by simply babysitting Wei Yan through the level. This one is even easier than most, as Wei Yan heads for the mission-ending target on his own.