The UK’s Household Cavalry tweeted a little Christmas present—and puzzle—on Christmas Day of a photo with six hidden snipers so well camouflaged that they “will test your powers of observation,” the cavalry promised.

It said it would reveal the answer on Boxing Day, Dec. 26, but the puzzle apparently proved too hard, so they put out another photo later in the day with the locations of the six riflemen partially revealed.

They asked people to write in the comments how many they found.

“If I find one it’d be a miracle!” wrote one Twitter user.

“No!!!” wrote another.

“If you can see them, they all failed in their mission …” another wrote.

The pictures were taken in July on Salisbury Plain, one of Britain’s best-known open spaces.

This isn’t the first time the British military has put out photos like this. Check out these two photos that were taken last July in Brunei that the Army in London posted to its Facebook account in February. Can you spot them?

They’re pretty good at hiding themselves, right?

Here are a few more of their behind-the-scenes camouflage pictures:

2017 Year in Review