The prospects for success of the Turkish military and allied rebel groups in the three day-old Operation Olive Branch (called Hunting the Wolves by the SDF) are not good. This assessment is based on troop strength, fighting style, and terrain.
Troop strength is not the endgame of a battle, but it can be a strong factor. Even with superior weaponry and positioning, having less troops than the enemy makes it harder to win. In the invasion of Afrin, Turkey is reportedly fielding 6,400 of its own soldiers alongside rebel fighters numbering between 10,000 and 25,000. From this we can safely estimate a total of 23,000 Olive Branch fighters. On the SDF side are 8,000 to 10,000 according to the PM of Turkey. Although 10,000 seems too small a number, this estimate is fair.
Purely by statistics, the rebel forces outnumber the SDF 2-to-1 in this battle, but many more factors need to be accounted for. The rebel fighting style is not well-suited to the task at hand. Massed infantry assaults with heavy machinegun fire worked well against Syrian government forces in the past, but that was on flatter terrain against a state army. In particular, the Kurdish forces’ guerilla tactics and mountain warfare can be difficult to overcome by a force unaccustomed to this kind of fighting. The SDF has had four years to train in anticipation of a rebel invasion, and Afrin’s military forces are primarily engineered towards repelling such an invasion.
Terrain is another often-overlooked factor that can make all the difference in an otherwise evenly-matched battle. In the case of Afrin, the terrain is clearly on the side of the SDF, as they hold the high ground of defensible mountain formations which overlook key roads and towns. The engagement at Bersaya Mountain, where rebel forces sustained many casualties before taking the top of the ridge, shows that the Kurdish forces can resist well when defending an elevated position. Besides, the battle for Bersaya was heavily assisted by Turkish Army artillery and grenade launchers, which will not be able to reach into the interior of the canton in future battles around Afrin town.
Overall, rebel groups should not expect an easy or quick victory, or a victory at all. If Olive Branch does succeed, it will likely take many months before Afrin town is captured, and even longer for the rest of the area to be cleared. A taxing, protracted battle ending in a stalemate is far more likely.