How are two-front wars won?

[I'mNotDedalus]

The two-front war often connotes disastrous ruin, with Napoleon and Hitler touted as the strongest examples of proof. But I can immediately think of two cases where history disagrees: The US concurrent victories in Europe and the Pacific during the Second World War, and Israeli victories during the 1948 War, the Six-Day-War, and the Yom Kippur War. I admit ignorance about most of Asia's military history, so I could very well be missing some other examples. Furthermore, Rome's victories against Philip V and the Carthaginians during the Second Punic War might be another example, but I want to focus on modern warfare.

Is there a pattern, here? Is victory in a two-front war secured by larger troop levels? Technological superiority? Aggressive/Defensive policy motivations? Or is there no pattern, at all? Why are some two-front wars lost but others won?