11 crucial facts to understand the Israel-Gaza crisis

But there's a ton of backstory that's necessary to understand the bigger picturen of Isreal-Gaza crisis.

As you can see on the above map, Gaza is separate from the other major Palestinian population center — the big yellow blob to the east of Israel, the West Bank. So despite both territories being largely populated by Palestinians, they're basically separate geographic entities.

The Gaza Strip is 146 square miles, and has a population of about 1.6 million. That's a lot of people in a very small area. For perspective, Philadelphia is about 142 square miles and has about 1.5 million citizens. In other words, the entire Gaza Strip is basically as dense as a major American city.

Until 2005, Israel occupied Gaza in the same way that it occupied the West Bank. That included Israeli military bases and settlements, communities of Jews living inside Palestinian territory.

In 2005, Israeli Prime Minister Ariel Sharon decided to withdraw from Gaza. Sharon, a longtime hawk and skeptic of Palestinian independence, had concluded that the Israeli occupation was no longer in Israel's interest. Sharon withdrew Israeli outposts and uprooted about 10,000 settlers. It was a hugely controversial move inside Israel, particularly on the political right — the current Israeli Prime Minister, Benjamin Netanyahu, quit the government in protest.

Hamas is, according to its charter, the Palestinian branch of the Muslim Brotherhood — an Islamist group that operates around the Muslim world, and one that nominally ran the Egyptian government for about a year recently. Hamas isn't controlled by the Egypt-based brotherhood leadership, but they have close ties. Unlike many Brotherhood branches, though, Hamas also has a militant wing: the Izz ad-Din al-Qassam Brigades.

Hamas sees itself as the representative of the Palestinian people — and, in a sense, they're not totally wrong. Prodded by the George W. Bush administration, the Palestinian Authority held popular elections across the West Bank and Gaza for the Palestinian legislature in 2006. Hamas won a slight majority.

There are other militant groups in Gaza, most notably Palestinian Islamic Jihad. These groups are even more radical than Hamas and are wholly committed to violence rather than to politics as the main tactic in their struggle with Israel.

Since 2007, Israel has maintained a blockade of Gaza. It severely restricts all border crossings in territory it controls and naval pathways into the Strip. The blockade restricts access to food, water, electricity, gas, construction materials, and other necessities. It's not that Israel doesn't let any of those things into Gaza; it's that it bans many products and regulates the flow of others pretty tightly.

Since Israel's 2005 disengagement, Israel and Hamas have fought three separate wars: in 2006, in 2008-9, and in 2012; Israel invaded Gaza in the first two but only bombed in the third. The 2006 war was triggered by Hamas kidnapping a young Israeli soldier, much as the current crisis was triggered by the kidnapping and murder in the West Bank of three Israeli students. They were killed by men who Israel believes were Hamas operatives.

Iran is arguably Hamas' most important international patron. For many years, Iran supplied Hamas with cash and advanced rockets. But, in 2012, Hamas and Iran went through something of a divorce over the war in Syria. Iran backs Syrian dictator Bashar al-Assad, an Alawite Shia, against the popular Sunni rebellion, which the mostly-Sunni Palestinians largely support. Hamas refused to take Assad's side, so Iran cut off cash shipments in late 2012.

Because Hamas can't get much through the Israeli blockade, they've developed an alternative means of resupplying Gaza: tunnels into Egypt. Gazans dig under the Egyptian border and pop out past border guards on the other sides. Smugglers supply them with goods that Israel can't or won't let through.

There's only one major supply route to Gaza that isn't a tunnel or Israeli-controlled: the Rafah crossing into Egypt. Currently, Egypt heavily restricts the flow of people and goods in and out of the crossing. The Muslim Brotherhood is the leading Egyptian opposition group, and the Egyptian government has little desire to help out their Palestinian brethren in Hamas.