Early law and practices for protecting nationals abroad reflect the fact that the first nation-states were few in number and shared in some degree heritages derived from civilizations rooted in Judeo-Christian and Greco-Roman traditions—and thus some commonalties in law. This encouraged European nations—and the United States after independence—to agree that their nationals should submit to the full operation of local law whenever their nationals traveled in one another's domains. Generally speaking, these nations acted on the presumption that their nationals would be accorded justice. However, if their nationals suffered wrongs and found no relief in local remedies, these nations reserved rights to intervene on their nationals' behalf.
However, the system was scarcely trouble-free. The United States, for example, quarreled with European states when the latter imprisoned immigrants who had returned from America to visit family. The returned immigrants were often charged with having failed to meet their military obligations. At issue in such cases was whether the immigrants, while in the United States, had established indisputable claims to American citizenship and whether the United States could legitimately spring to their defense.
Sometimes disagreements generated serious tensions. In 1891, for example, American sailors on shore leave in one of the seamier sections of Valparaiso, Chile, were set upon by a mob that killed two of the sailors and injured others. Chile dismissed the incident as an unfortunate drunken brawl, but the United States charged the Chilean government with complicity in the clash. The assault had been a premeditated way of expressing Chilean resentment of the United States. The exchange of recriminatory charges escalated and led the United States to threaten war. At that point Chile met American demands for "prompt and full reparations" by issuing a formal apology and paying $75,000 in damages.