I spent a decent chunk of 2009 rolling down the roads of western Iraq, working with Iraqi police, and trying not to get blown up. On my most recent birthday, I tried to reflect back on the birthday I spent there near the end of that deployment. How different it was. But, looking back, I couldn’t even tell you where I went that day. Fallujah? Ramadi? Habbaniyah? It’s hard to tell. It’s been more than a decade since most of us were there and, while some things are still quite sharp, the day-to-day stuff is getting fuzzy.

I did remember a running joke that would come up now and again, though, because it was exactly the type of thing that would come up on a birthday in Iraq. Occasionally, when the opportunity seemed right, someone would wonder aloud, “Why are we here again?” And the answer, delivered dryly, was always some refrain of: “Oh, yeah. Oil.”

It’s not like we were being clever. Everyone knew it. The old CENTCOM commander, John Abizaid, had said it quite clearly in 2007: “Of course it’s about oil; we can’t really deny that.” Alan Greenspan had agreed, and Chuck Hagel directly confirmed it: “People say we’re not fighting for oil. Of course we are.”

It’s the reason we’ve cared about the Middle East for decades. It’s almost certainly the reason I spent parts of 2012, 2013, and 2014 in Afghanistan, too. Al-Qaeda would have likely never existed were it not for the U.S. obsession with oil, considering that the chief popular complaints that al-Qaeda exploited centered around our actions in the Middle East. Without al-Qaeda, we would have cared about Afghanistan and the Taliban about the same amount we care about Eritrea and its repressive king. Which, of course, is not at all.