See also London's Daily Mail, "Picture of Evil: Bloodthirsty German Al Qaeda Fanatic Poses With 2ft-Long Knife for Beheading British Soldiers in Afghanistan."
The knife is too cumbersome to use in battle - but could behead or dismember any hostage his terror group grabs.
The insurgent, also seen sitting with an AK47 rifle, belongs to one of Osama Bin Laden's "foreign legions" fighting in Afghanistan.
He appears in a new terror video posted online and vows to use the huge blade to achieve a victory for Islam.
The bearded thug was identified as "Abu Askar the German".
Last night a military source warned: "If anyone needed reminding, this is the face of the enemy."
Terrorism expert and author Chris Dobson said: "The bloodthirsty threat of Abu Askar the German and his giant cleaver is plain - anyone who opposes us will lose their heads. Fanatical Islamic Jihadists have a record of beheading captives and boasting about it to cause fear among their enemies.
"Abu Askar and his knife are undoubtedly part of the 'war of the mind' the Jihadists are waging against the West.
"But they also reflect a growing confidence, especially among home-grown terrorists, that the West is becoming vulnerable."
Related: As Obama Dawdles, Taliban Mount Terrorist Offensive Across South Asia