JERUSALEM—Many historians call Israel's Six-Day War the first pre-emptive war of modern times. It redrew the map of the Middle East and changed the balance of power between Israel and its Arab neighbors, but 40 years later most of the new issues it created and the old ones it didn't resolve remain contentious.

For weeks before June 5, 1967, Israel's neighbors, particularly Egypt, had suggested that they were planning some sort of aggressive action.

Egypt ordered the United Nations to abandon outposts that had been set up after a 1956 war to guard against Egyptian-Israeli clashes along the border. Tens of thousands of Egyptian troops had massed in the Sinai. The Egyptian government banned ships bound for the Israeli port of Eilat from using the Strait of Tiran, cutting off a large percentage of Israel's oil imports.

Syria had been sponsoring Palestinian attacks into Israel for years and had been shelling Israeli settlements in the Galilee from positions on the Golan Heights. A border incident that April had led to an aerial battle in which Israel shot down six Syrian aircraft. Syrian snipers regularly harassed Israeli farmers.

Jordan, which controlled the West Bank and East Jerusalem, had complained about Israeli assaults on Palestinian villages in the West Bank, which Israel said were refuges for terrorists. On May 30, Jordan signed a mutual defense pact with Egypt.

With all signs pointing toward an imminent Arab attack, Israel—outnumbered and surrounded—decided not to wait. On June 5, it launched a massive air attack on Egypt's air force, destroying virtually all of its planes on the ground. At the same time, Israeli ground forces moved into the northern and central Sinai Peninsula. Within two days, the Egyptians had retreated across the Suez Canal.

Jordan had responded to the initial Israeli attack by sending aircraft to bomb Israel and moving troops into some parts of Israeli-controlled West Jerusalem. Israel responded by surrounding East Jerusalem and attacking on June 6. By June 7, Israeli forces had captured East Jerusalem and much of the West Bank.

While Israel had destroyed most of Syria's air force on June 5, ground fighting for the Golan Heights didn't begin until three days later. Without an air force, Syria couldn't defend its troops from Israeli air assaults, and the Golan Heights were under Israeli control by June 10.

A cease-fire was signed the next day. The war had lasted just over 132 hours.

Since then, Israel has made peace with Jordan and Egypt and returned the Sinai to Egyptian control.

But its occupation of the West Bank remains a contentious issue. Though the United Nations has deemed the Israeli settlements illegal, they've shifted the political debate and made it more difficult to establish a viable Palestinian state, something that the 1993 Oslo Accords called for.

More than 240,000 Israeli settlers now control about 40 percent of West Bank land, according to Peace Now, an Israeli advocacy group. While Israel forcibly removed all its settlements from the Gaza Strip two years ago, the number of settlers in the West Bank is still growing.

Israel also has said it will never allow the Palestinians to establish a capital in Jerusalem, something Palestinians argue that they have the right to do.

In 1981, Israel essentially annexed the Golan Heights, an area that Syria still claims. Since then, the idea of a peace agreement that would include an Israeli withdrawal has been mentioned often but has never been the topic of serious negotiation.