The nitrate region extends along the narrow desert coast of the Pacific for three hundred and fifty miles. Peru owned the northern one hundred and fifty, and prior to 1866 Bolivia claimed the remainder. After the discovery of the precious mineral the industrious and energetic Chileans crowded up the coast, while the Bolivians were shut in behind their high Andes. Chile insisted that her true boundary lay as far north as the 23d degree, and took vigorous measures to safeguard the interests of the Chilean nitrate companies. In 1866 Bolivia reluctantly made a treaty by which the 24th degree was agreed upon as the formal boundary, although the Chilean miners were allowed to continue their operations in the productive regions north of that line and their taxes were not to be increased without their government's consent. This treaty gave rise to constant disputes, and as the nitrate, silver, and copper business of the neutral zone became more profitable, the Bolivian government pressed harder for a larger revenue. The Peruvian government had planned to secure a control of the output by the state purchase and operation of nitrate properties, and such a trust would prove ineffective unless the Bolivian government had a free hand with the Chilean companies. In 1872 Peru and Bolivia made a secret treaty of alliance. Its provisions soon became public, and Chile not unreasonably believed it to be aimed especially at her miners' operating on Bolivian soil. She promptly began purchasing iron-clads. It was a favourite saying of old Marshal Castilla that when Chile bought a battle-ship Peru should buy two, but the Lima government was too poor to follow the good advice, and the fatal year of 1879 found her naval force inferior to that of her rival. At this juncture the Bolivian congress voted not to ratify a treaty negotiated with Chile four years before, and passed a law imposing heavy taxes on the nitrate business. The Chilean companies protested and resisted; their government backed them up, and sent a fleet to protect their interests. Enraged at the seizure of her ports, Bolivia declared war in March, 1879. Peru could not be expected to remain quiet. Not only was she bound by the solemn agreement of the treaty of alliance, but she had an imperative selfish interest in preventing the disputed nitrate territory from falling into Chile's hands. She began to gather an army on the southern frontier, but she was illy prepared for war and Chile knew it. Her offers of arbitration were promptly rejected; the Chilean government had determined to strike both allies at the same time, and presented an ultimatum, demanding that Peru abrogate the secret treaty, cease warlike preparations, and remain neutral in the war with Bolivia. Failing immediate and categorical compliance war was declared in April.