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It's important to note that if the attack dislodges the supporting unit, the support is dropped.

Nevvermind. I figured it put. RR is reliability rating. So, in this case joining requires that you have a 30% reliability rating.

In a World Diplomacy game description, I see "RR30%".
Can someone help out a newbie and explain what that means?

I'm new to online Diplomacy, but have experience playing Dip I. Ancient times; back when you either played face-to-face or via postal mail (aka snail mail). Different zines had different house rules, but I remember most had some sort of standby moves system. When a player didn't submit moves by the ...