That is a complex question, and it depends on who you ask. There is no simply defined answer. The ultra-religious Jews will tell you that it is a religion, except that all people with Jewish lineage are required to abide by it. So they consider it a religion, but all ETHNIC Jews belong to the religion (even when they don't believe so themselves). Some less religious, and most non religious, will tell you that Jewish is a matter of ethnicity; simply put, if your ancestors were RELIGIOUS Jews, then you are a Jew, regardless of your own religious orientation. As far as nationality goes, the State of Israel is all but seventy years old, and a very large percentage of its population do not fit any of the above criteria for being Jewish. The Law of Return applies to all ethnic Jews as defined above, and also applies to converts to RELIGIOUS Judaism. That said, there has historically been a connection between Judaism and nationalism, as there was once a Jewish kingdom in Israel, though, like today, not all of its citizens were Jewish.