It is not someone's position or place to question or defy a situation, order, or the way things are done. Taken from a line from Lord Alfred Tennyson's 1854 poem "The Charge of the Light Brigade," describing the British cavalry as they obeyed orders to ride into certain death in the Crimean War. Can also be phrased as "ours not to reason why." It is a difficult balance to strike. We must have well trained soldiers who obey orders, theirs not to reason why, yet we can't have those willing to perpetrate war crimes or follow foolish orders to their own deaths, either.