A 19th-century revolutionary campaign across the Andes

In January 1817, a band of soldiers particularly ill-suited to the cold, breathless conditions of the high Andes tramped over lofty passes from western Argentina into Chile. Not only had they little or no experience of the effects of altitude, around half were not of South American or even Spanish descent, but African. Yet these men, fighting under an ageing general with an audacious plan, achieved victories that swung the balance in favour of independence for Chile and Peru.

In the mid-1810s, the future of an independent Latin America was poised on a knife-edge. Spanish royalists had quashed patriot risings across the region. The fractious, penniless United Provinces of the Río de la Plata – roughly speaking, covering what’s now Argentina and Uruguay plus parts of southern Bolivia and Brazil – headed by Buenos Aires, barely held the Spanish at bay in Upper Peru.

Into the picture stepped José de San Martín, a middle-aged, austere and iron-willed career soldier, now a general of the province’s army, with an audacious strategy: to march west over the Andes into Chile, surprising and crushing royalist forces there, then sail for Lima