As a general rule of thumb if you come upon a 1 on 1 it is always good to ask on country if that person would like help in the fight before just jumping in ah la MA style.
Frank,
If you want to fight in uninterrupted 1 versus 1 fights the best place to do that is the dueling arena. HTC conveniently created a terrain full of airfield pairs that are perfect for doing just that. You are under no obligation to ask permission to enter a 1 versus 1 fight in the Axis versus Allies Arena. There are folks who will get upset with you if you interrupt them but it is an imaginary rule. Just examine the name of the arena:
Axis 9. an alliance of two or more nations to coordinate their foreign and military policies, and to draw in with them a group of dependent or supporting powers.
10.the Axis, (in World War II) Germany, Italy, and Japan, often with Bulgaria, Hungary, and Romania.
The word Allies is obviously plural but here is the definition just in case
n. pl. al·lies1. One that is allied with another, especially by treaty:
2. One in helpful association with another:
3. Allies
a. The nations allied against the Central Powers of Europe during World War I. They were Russia, France, Great Britain, and later many others, including the United States.
b. The nations, primarily Great Britain, France, the Soviet Union, and the United States, allied against the Axis during World War II.
The name of the arena implies teamwork so feel free to pounce on that low and slow anchored fight.