Major Mitchell- thank you for your response. I made each of the agreements for a specific purpose. The alliance was made with the player to the west to combat a common foe to the north. The non-aggression pact with the player south of me, to buy time while I battled a player to the east. When the player from the south attacked my western ally, I was concerned that they would have to pull resources from our northern campaign. It is in my best interest to continue to work with my ally fighting in the north and avoid a shooting war with the player to the south.

You do what you perceive to be in the best interests of the nation you have in the game.

Yavuzovic - thank you for your response.
Your conclusions are correct. I suspect one of the reasons player”B” is upset is that is they do not want war with both of us.

I should have made clear when creating the non-aggression pact that player “A” and I had an alliance. An attack on player “A” that causes resources to be pulled from the battle elsewhere impacts that alliance.

Crazy Anglican - thank you for your response.
My logic was in line with your comments, although not as elegant.

I felt a “move” or “support move” was an aggressive act and would violate the pact. But a “support hold” is a defensive move and did not.

Player “B” was unimpressed with my logic and felt they had been betrayed. Your point on specific territory restrictions is on point as well and likely would have prevented the problem.

Easy,
If it serves B's interest, you gave them an excuse for a war.
If B prefers staying in peace, then you are fine.

I would imagine that the terms of the non-aggression pact would be more clearly spelled out at this point, but the following argument could be made:

"I agreed to a non-aggression pact with you and have not acted aggressively toward you, I was asked to support hold a unit. The fact that you decided to attack a unit that I was supporting (if anything) means that you broke the non-aggression pact (but I forgive you since I see that it was an accident)"

I would furthermore point out (We have decided on neutrality towards one another, if I simply stopped supporting units in case there might be a change that you would attack them then we are moving into the realm of alliance rather than neutrality)

Regardless I would probably opt for explicitly defined demilitarized zones rather than a blanket non-aggression pact.

Then player "B" is to blame for this mess.

Thanks for your response.
Player “B” was afraid that I would tip off player “A” of their plans to attack.

"B" knew this and should've asked before attacking "A".

Thanks for your response.
I tend to agree that specific clauses are very helpful in non-aggression pacts. What placed me in a difficult spot was that I had an alliance with player “A”, where we were fighting shoulder to shoulder against player “C” on the other end of the board. When “B” attacked “A” I was between a rock and a hard place.

Well with the stipulation that "context is king" ...

But if I had someone make a non-aggression pact with me and then support hold vs me I would be pretty ticked off. While you are not directly attacking me you are helping an enemy of mine, which is what I would consider a hostile act and I'd considered it a breech of our agreement.

I'd look at a "non-aggression" pact as a "you don't meddle in my stuff and I won't meddle in yours." However it is for this reason of "what we do we mean by 'non-aggression pact'?" that I try to get specific when making these kinds of deals, so we're both clear on what's being agreed on

I agree that the terms have no clearly defined meaning. That is why I posted the question, to see where other players come down on their meaning.

To answer your question, player “B” was not happy.

A strange question! Terms like "non-aggression pact" or "alliance" don't have any kind of consistent precise meaning. Perhaps it would be better to ask: what will B think and do if you support hold the army?

Diplomacy players routinely enter into alliances (working with another player toward a common goal) and non-aggression pacts (agreeing to leave each other alone). So assume you have an alliance with player “A” and a non-aggression pact with player “B”. Now “A” and “B” go to war. Player “A” (who you have the alliance with) asks you to support hold an army he expects player “B” to attack. Since “support hold” is a defensive move, does it violate your non-aggression pact with player “B”?