In 2011, a 24-year-old history buff named Alwyn Collinson had a simple idea: Tweet the Second World War as if it were actually happening, live, today. The goal, as he described it then to the Telegraph, was to "help people feel like they're there," sprinkling his coverage of the war with period photographs and little anecdotes to flesh out the major plot points, which began with Hitler's invasion of Poland in 1939.

Now, after years of tweets about Rommel in Africa and the Battle of Britain, Collinson has finally reached a pivotal moment in the war's history. He's live-tweeting D-Day on its 72nd anniversary, down to the exact hour that the invasion began. It's an amazing achievement because it means followers of @RealTimeWWII are now re-living D-Day after a long period of enormous buildup.

Some of Collinson's livetweets bring back iconic images of the day. If you've seen "Saving Private Ryan" or "The Longest Day," these will definitely be recognizable.

But one of the things that makes @RealTimeWWII so compelling is the way it elevates lesser-known facts and photographs, lending the sense that you're watching more than just a documentary or reading a textbook that simply goes through the motions.

Live-tweeting D-Day isn't a new idea. But what makes @RealTimeWWII unlike the others is that Collinson has been chronicling the entire war with his feed, and it has finally built up to this major historic day.

The Allies battled the Axis for another year after the initial invasion of Europe. And so too will Collinson soldier on — but today marks an epic moment for a commensurately epic project.