Accordingly, they should take into account the public impact of their statements. They need to realize how such public statements undermine trust between the military and civilian authorities. And finally, they must answer this question: Is it proper for unelected military officers to undermine duly elected officials, especially when they use the sort of contemptuous language that would be impermissible were they still active-duty?

The key to healthy civil-military relations is trust, which is necessarily based on mutual respect and understanding between civilian and military leaders. Trust requires the exchange of candid views and perspectives between the two parties as part of the decision-making process.

As citizens, we should insist that military officers present their views frankly and forcefully throughout the decision-making and implementation process, something the Joint Chiefs of Staff failed to do during the Vietnam War. The give-and-take between civilians and soldiers can be contentious. Indeed, it should be.

In the case of General Milley, he should have made his objections known to the president in private. But public attacks on an elected president by retired officers and the threat of resignation by high-ranking officers undermine trust and poison civil-military relations. Toxic civil-military relations are something no citizen should desire.