Three armies clashing over Northern Italy... a history classic
Napoleon's 1796 campaign is just one of the many occurrences of a classic historical pattern. Two hegemonic superpowers - France and Spain, or France and Austria (the Empire) - engaging in battle over Northern Italy, and a smaller player - Savoy / Piedmont - joining either side, sometimes decisively tipping the balance in favor of either superpower.
Both major players needed, and often actively seeked, the alliance of the Duke of Savoy, later King of Sardinia: the gate guardian of the Alps, the lord of the vital mountain passes across the French-Italian Alps. Promising him a rich booty in return for his allegiance... but with the mental reservation not to keep the promise at the end of the war. On his part, the Duke's interest was lying in playing France and Spain/Empire off against one another, in the meantime surviving the clash of the giants avoiding being squeezed and trampled to death in the process and trying to carve his way into grabbing portions of Italy, a little at a time.
During the Renaissance wars between France and Spain over Italy, the poorly armed and defended Duchy of Savoy came within an inch of being wiped out and absorbed by France. Refounded in 1562 by the Iron Head Duke Emmanuel Philibert, it had learned the lesson and Piedmont gradually became a tough nut to crack. About 1620 the Duke managed to finish a war with the Spanish Empire in a draw, which was a phenomenal David vs. Goliath achievement.
The 1792 - 96 situation, although apparently reproducing the usual pattern, is however different. France is no longer the Ancien Régime member of the European community of balanced powers, but a powerhouse of national revolution flashing beams of tremendous, history-changing energy across Europe. And Austria, facing that juggernaut and having grudgingly yielded to Piedmont chunks of its Italian possessions all over the 18th century, is lightyears away from accepting to spend much sweat and blood on defending its junior partner.
As importantly, while two of the armies still belong to the 18th century warfare era, the third one in the field - the French army - is making new military history by rapidly outrunning, outgeneraling and outfighting its opponents by employing unprecedented tactical and operational proceedings.