When is a tree not a tree? Well, that’s not quite the esoteric problem you might imagine. Actually, it’s one grounded in fact…and deadly serious fact at that because, during World War One, a man’s life might depend on the answer to that very question.

Both the British and the Germans vied in the cunning methods they deployed to outwit and kill each other during the war. For example, underground mines were regularly placed beneath enemy positions to blow soldiers to smithereens. In fact, the British used a series of such mines at Messines Ridge in 1917. They caused a massive explosion that killed ten thousand Germans and created a blast that was heard by Lloyd George in Downing Street.

Similarly, the British came up with an enormous and deadly hidden flame thrower that rose up from the ground and devastated enemy positions. A less spectacular weapon, but one that was just as lethal for its victims on the Western Front, was the use of artificial trees on the battlefield. Yes, you read correctly.

Under cover of darkness, real battle-scarred stumps in no-man’s land would be replaced with artificial replicas. Made of wrought-iron and steel, these were ingeniously camouflaged and were used as observation posts from which to spy on and snipe at the enemy.

The British tasked special groups of Royal Engineers to carefully select a real tree on the battlefield. The ideal ‘candidate’ would be dead and often bomb scarred. The tree would be meticulously measured, photographed and sketched from all angles.

The information was then sent to a workshop where artists constructed an artificial tree of hollow steel cylinders, inside which was scaffolding for support and enough room for a sniper or observer to climb.

Then, under cover of night, the team would cut down the real tree, dig a hole in the place of its roots and insert the replica.

Come daybreak, the enemy would not know the difference and instead of a harmless stump there would now sit a deadly sniper tower. Simple, but very effective…

Firing from these perfectly camouflaged structures, snipers from both sides claimed many victims. The Germans called them ‘Baumbeobachter’ – or ‘tree observer’ – the British christened them ‘O.P. Trees’. Presumably, the initials stood for ‘Observation Post’.

London’s Imperial War Museum houses several sketches depicting camouflaged trees, including work by the artist Leon Underwood, who was one of the original camoufleurs.

And next summer, you can see one of these intriguing structures for yourself if you visit the Museum. An original camouflage tree, believed to be the only one of its kind, will be on display there at the new First World War Galleries section.

Back in 2008, a reconstructed tree was put on display by the Australian War Memorial in Canberra after it was captured by Australian troops in 1917.

According to Diane Rutherford, who wrote about it on the memorial’s website, the tree was ‘from Oosttaverne Wood, also sometimes spelt Oostaverne Wood, near Messines in Belgium.

‘We don’t know when the tree was erected in the wood, but it could have been used by the Germans up until June 7, 1917, when the Oosttaverne area was captured by the British during the Battle of Messines.

‘It was hidden among a group of real trees in the wood and would have been difficult to spot as a fake – especially from a distance.’

We’ve had World War One and World War Two, now, thanks to the devious military mind, we can look back in horrid fascination at the heartache wrought by World War Tree…