1817
Crossing of the Andes
The setting
Andes mountains between Mendoza (Argentina) and Chile
High Andean passes up to ~4,000+ m, extreme cold, thin air, and barren ground
Reveal the outcome
Recorded sideArmy of the Andes (Patriots)
Recorded resultSuccessful crossing; campaign victory at Chacabuco
San Martín led the Army of the Andes across multiple high passes in a meticulously planned logistical operation, using feints and disinformation to scatter royalist defenders, then reunited his columns to win at Chacabuco and liberate Chile.
How the atlas explains it
Exhaustive logistical preparation and multiple coordinated routes let the army survive the mountains, while a deliberate deception campaign convinced the royalists to defend the wrong passes, surrendering surprise to San Martín.
What followed
A logistics-and-terrain masterpiece that made the liberation of Chile possible and set up the maritime campaign against Peru; one of the most celebrated military feats of the wars.