Dual citizenship has become increasingly widespread today as migration levels have increased. For many people who travel or have family in different countries, having multiple passports is a great convenience. But if one takes national identity seriously, it is a rather questionable practice. Different nations have different identities and different interests that can engender potentially conflicting allegiances. The most obvious problem involves military service: if the two countries of which one is a citizen go to war with each other, one's loyalties are automatically in question.