One Army Must Stand Guard
One Army Must Stand Guard is a setting that can be configured by game creators. When enabled, players must leave one army behind on every territory whenever they attack, transfer, or airlift armies out of a territory.
For example, if you have 5 armies on a territory, only 4 would be eligible for an action, and the 5th must remain on the territory to guard it. However, if this setting is left unchecked, then all 5 armies would attack or transfer, leaving the territory from which you attacked with zero armies; however, you will still retain ownership(ie, it has your color and counts towards your bonuses).
For example, you own a territory named Territory A. It currently has 10 armies. if you wish to attack Territory B from Territory A and-
YOU HAVE ONE ARMY MUST STAND ENABLED(Checked): Only 9 armies will attack Territory B. The last army MUST stay on territory A to keep it yours- there is no way around this.
YOU HAVE ONE ARMY MUST STAND DISABLED(Unchecked): All 10 armies will attack Territory B. Although you will have 0 armies left on Territory A, it will remain yours.
RISKS AND BENEFITS OF THIS STRATEGY: Risk- It will allow for enemies to easily take over all of you land, as they will face no resistance Benefit- You can do the same to your enemy, and it will leave you with more armies to attack with.
In short, this is a high stakes strategy, but one that can pay off well- or ultimately lose you the game.
Example image of One Army Must Stand Guard in action