Expanding on WIA's great summary a bit: the religious reason, for the Jews, comes down to something of a split in Jewish thinking following the Holocaust. For many Jews living in Israel or heavily supporting Israel, it is not just about culture, it's about the Messiah.
As a starting point, consider Christianity. Judaism has a long tradition of teachings and prophets that one day a Messiah would come who would raise the Jewish people -- who think of themselves as the Chosen people of God, the Israelites - so they'd have a kingdom of their own which God would support, a holy kingdom which they call Zion.
Christianity, which is an outgrowth of Judaism, believes that Messiah has already come: Jesus Christ, who is seen as not a secular ruler or king as such, but rather a spiritual Messiah, a saviour of mankind from original sin. Judaism, in summary, does not accept Jesus as the Messiah (basically because there are several prophecies he is said not to have upheld, but more basically because he didn't unload a can of angel-backed military whoopass on the occupying Romans at the time of his arrival) and Judaism says it is still awaiting the coming of its Messiah.
Here's where the religious element plays into it: there is a disagreement in Judaic religious circles about whether the Messiah, when he comes, will establish Zion on Earth ... or whether it's the responsibility of the Jews at large to create Zion, the holy city, on Earth so it's waiting for the Messiah when he shows up. Added to that there's the issue of where and what Zion is or should be: is Zion a literal place (compare the "kingdom of God" that Christianity often refers to as a spiritual realm rather than physical) and if Zion is a literal place, should it not be in Jerusalem, the city promised to Judaism as its centre according to its historical traditions?
Added to that was, like it or not, the Holocaust in WW2. Six million Jews dead was a profound blow to Judaism at large; it took on almost a religious significance for some elements, a sign that something fundamental had to change in Judaism at large. Indeed the name Holocaust is one that comes from Judaism itself - it's the word for sacrifice, a burning of a sacrificial animal on an altar, sometimes called the Shoah, the destruction in Hebrew.
One vector of that belief (which also held a practical dimension) was that Jews would never be safe in the world unless they had a nation of their own, or lived in a country that was historically theirs. The last Jewish nation in the world had really been the Khazar nation in the Middle Ages; as one book put it, there hadn't been a Jew for roughly two thousand years who could look for a soldier and expect to find one that shared his allegiance or his religion. Hence the large-scale immigration of the Jewish Diaspora around the world to Palestine, to lands that historically had been Jewish in the past - as well as the standing invitation for people of Jewish descent to "return", i.e. immigrate, to Israel.
And thus, Zionism: the idea that Israel is not just a nation, a refuge for Jews, but that it's a God-ordained holy nation for Jews to be built so the Messiah can finally turn up.
The establishment of the State of Israel in 1952 was as much an attempt at a stop-gap solution as any sort of positive manipulation of boundaries in that area (although the colonial powers were pretty shit at that, too).
If practically you wouldn't want to be surrounded by enemies as a Jew: well, Israel more or less throughout its history was surrounded by enemies according to the Old Testament. Wander through the OT and it's pretty hard to find a period when Israel's kings weren't fighting someone or other; hell, even on arrival back from Egypt under Moses, Israel basically pushed out (on God's command) all the inhabitants of Israel who were already there.
And Israel has always enjoyed (a) serious support from the US and (b) incompetence among its Arabic conventional enemies. I mean, the war in 1967 was a wash. It's also called the "Six Day War" because it only took Israel six days to win it. Egypt, Jordan, and Syria all declared war and advanced on Israel, and Israel pushed back all of them. They wiped out Egypt's entire air force in pre-emptive strikes and pushed the Egyptians right back across the Sinai, all the way over the Suez Canal. Although note also that wasn't the start of the conflict: the Arabs had been trying to destroy the Israeli presence in Palestine since 1948.
RooshV.com