It's precisely 100 years since the first tanks went to war in the Battle of Flers-Courcelette in France. They were originally thought of as "landships", but the name "tank" was adopted as a security measure, to conceal their true nature. The Telegraph reports:
Tanks were first used on 15th September 1916 in an attack to destroy German strongpoints between the villages of Combles and Courcelette.
They had been developed in only two years with support from Winston Churchill at the Admiralty in an attempt to break the bloody stalemate of trench warfare and were originally known as landships.
Of the 49 supposed to be deployed for their first battle, only 32 made it to the start line and only nine made it across no-mans land to the German lines.
There's more at the link.
Here's footage of that first attack by Mark 1 tanks. It's silent, so don't adjust your volume.
Here's an excerpt from a BBC documentary about tanks, including World War 1 footage.
To mark the centenary, a Mark IV tank dating back to 1917 was driven into Trafalgar Square in London.
Today's tanks, for all their sophistication, are still fundamentally the same as those earliest models: a hull bearing a powerful cannon, mounted on tracks rather than wheels for greater cross-country mobility.