From the same link as above:
http://www.plainsboro.com/~lemke/risk/2v3
The first roll is the same as 2v2 since you have 1 attacking die versus 2 or more defending dice
Attacker: one die; Defender: two dice:
Attacker wins 55 out of 216 (25.46 %)
Defender wins 161 out of 216 (74.54 %)
3v3
The first roll is the same as 3v2 since you have 2 attacking dice versus 2 or more defending dice
Attacker: two dice; Defender: two dice:
Attacker wins both: 295 out of 1296 (22.76 %)
Defender wins both: 581 out of 1296 (44.83 %)
Both win one: 420 out of 1296 (32.41 %)
4v3
The first roll is the same as 4v2 since you have 3 attacking dice versus 2 or more defending dice
Attacker: three dice; Defender: two dice:
Attacker wins both: 2890 out of 7776 (37.17 %)
Defender wins both: 2275 out of 7776 (29.26 %)
Both win one: 2611 out of 7776 (33.58 %)
As for odds of winning if battled to completion, check out a table like the one at
http://www.datagenetics.com/blog/novemb ... index.htmlA 4v3 battle (3dice vs 3dice) has a 47.025% chance of success, but that's only if you keep attacking. In reality, you would stop at the first loss because the odds of attacking with 3 or less drops drastically. Sometimes its worth doing a 3v1 or 2v1, or even 2v3 or 2v2, depending on the circumstances.