With this mighty force at his back, yet knowing that the neighboring countries could eventually call into the field armies much larger in size equipped with repeating rifles and supplied with modern artillery, the "Jupiter of Paraguay" nevertheless made ready to launch his thunderbolt.
The primary object at which he aimed was Uruguay.

In this little state the Colorados, upheld openly or secretly by Brazil and Argentina, were conducting a "crusade of liberty" against the Blanco government at Montevideo, which was favored by Paraguay.

Neither of the two great powers wished to see an alliance formed between Uruguay and Paraguay, lest when united in this manner the smaller nations might become too strong to tolerate further intervention in their affairs.

For her part, Brazil had motives for resentment arising out of boundary disputes with Paraguay and Uruguay, as well as out of the inevitable injury to its nationals inflicted by the commotions in the latter country; whereas Argentina cherished grievances against Lopez for the audacity with which his troops roamed through her provinces and the impudence with which his vessels, plying on the lower Parana, ignored the customs regulations.
Thus it happened that obscure civil discords in one little republic exploded into a terrific international struggle which shook South America to its foundations.
In 1864, scorning the arts of diplomacy which he did not apparently understand, Lopez sent down an order for the two big states to leave the matter of Uruguayan politics to his impartial adjustment.

At both Rio de Janeiro and Buenos Aires a roar of laughter went up from the press at this notion of an obscure chieftain of a band of Indians in the tropical backwoods daring to poise the equilibrium of much more than half a continent on his insolent hand.