When in the summer of 2014 Germany started to deliver weapons to the Peshmerga - the fighting force of the autonomous Kurdish region in northern Iraq - the decision was highly controversial in Germany.
Up until that point a German government had never sent weapons into an active war zone.
Critics claimed the Bundeswehr (German army) would lose track of the weapons once they had been delivered and they could easily fall into the wrong hands.
The NDR investigation now shows that these fears were well founded.
In gun markets outside the capital Erbil and in second city Sulaimaniya, the broadcaster found Bundeswehr rifles and pistols for sale.
The letters ‘HK' in the serial number signifying production by German gunmaker Heckler & Koch, and the ‘Bw' for the Bundeswehr prove that the weapons are those delivered by Germany over the past 18 months, NDR claims.
A Kurdish fighter with a German-made G36 rifle near the city of Kirkuk, Iraq, in early 2015. Photo: DPA
According to one ex-Peshmerga fighter spoken to by NDR, a G36 rilfe (the standard Bundeswehr assault rifle) used to cost $4,000 (€3,690) but the price has collapsed in recent months because there are too many on the market.
In the market outside Erbil, the journalists were offered a G36 for between $1,450 and $1,800 (€1,338-€1662).
By last the summer the Bundeswehr had delivered 12,000 G3 rifles, 8,000 G36 rifles, and 8,000 P1 pistols to the Peshmerga. The ministry of Defence has previously has admitted it doesn't know which fighting units received the weapons.
The ex-fighter spoken to by BDR said he knew of around 100 of his comrades who sold their weapons and fled the war.
He himself fled to Germany after selling a Kalashnikov to finance the costs, explaining that he hadn't been paid a salary for almost half a year, after the Kurdish government's coffers were emptied by the fight against Isis and collapsing oil prices.
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Die LInke (the Left Party), who were strongly opposed to weapons deliveries to the Peshmerga when it was originally debated in the national parliament, have called for an immediate halt to further weapons deliveries.
“Weapon deliveries are a subsidy for the Peshmerga, so that they can finance their trips to Europe,” Jan van Aken from Die Linke (the Left party) told NDR.
The government laid blame for the leaking of German weapons with Kurdish authorities who had given pledges they would use them in accordance with international law.
Foreign Minister Frank-Walter Steinmeier has previously noted the contribution German support to the Peshmerga has played in them winning back territory in northern Iraq from Isis.