The German military has secretly admitted that it can't fulfill its promises to NATO, according to documents leaked to Die Welt newspaper on Thursday.

The Bundeswehr is due to take over leadership of NATO's multinational Very High Readiness Joint Task Force (VJTF) at the start of next year, but doesn't have enough tanks, the Defense Ministry document said.

Specifically, the Bundeswehr's ninth tank brigade in Münster only has nine operational Leopard 2 tanks — even though it promised to have 44 ready for the VJTF — and only three of the promised 14 Marder armored infantry vehicles.

The paper also revealed the reason for this shortfall: a lack of spare parts and the high cost and time needed to maintain the vehicles. It added that it was also lacking night-vision equipment, automatic grenade launchers, winter clothing and body armor.

The German air force is also struggling to cover its NATO duties, the document revealed. The Luftwaffe's main forces, the Eurofighter and Tornado fighter jets and its CH-53 transport helicopters, are only available for use an average of four months a year — the rest of the time the aircraft are grounded for repairs and rearmament.

"The state for all part-time forces are similarly worrying," Hans-Peter Bartels, parliamentary commissioner for the armed forces, told Die Welt. Opposition politicians blamed Defense Minister Ursula von der Leyen for allowing the military to deteriorate.

Von der Leyen should "ask herself what she's been doing for the last legislative period," Green party defense spokesman Tobias Lindner said in a statement.

"Apparently it is politically more opportune to constantly announce armament intentions and trend reversals, rather finally addressing the problems of spare parts and maintenance. Von der Leyen is fully and totally responsible for the current problems."

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More than just a money issue

Mark Galeotti, senior researcher and head of the Prague-based Center for European Security, said that "Germany's various military woes" were no secret to the rest of NATO. "For a long time, Germany has under-spent dramatically, and, let's be honest, wrapped itself in the mantle of its non-militarist foreign policy," he told DW, before adding that it had long been clear that the country hadn't been pulling its weight in the alliance.

According to the leaked document, the army would now be trying to cover its "capacity-relevant deficits out of the stocks of other units" — even though that would impact training and exercises elsewhere.

But Galeotti said that tanks present a particular technical challenge that could not necessarily be met just by throwing money at the problem.

"It's not just about buying the actual chunks of hardware, it's also about having precisely the spare parts, the technical infrastructure, the transporters, the refueling stations," he said. "Tanks are surprisingly temperamental for these great armored beasts of war, which is why this deficit can't quickly be made up, even if the money was available."

Given Germany's quasi-pacifist priorities (in NATO's military mission in Afghanistan, Berlin had a reputation among allies for keeping its troops out of harm's way), it is not surprising that the country should be cutting corners with tanks, Galeotti explained.

"Tanks are nothing but war-fighting instruments," he said.

"A soldier in a jeep can be used in humanitarian deployments in Africa, can do all kinds of things. A tank is just a tank. And it's that kind of outright military spending that is particularly where Germany has failed in the past two decades."

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The political trip-wire

NATO set up the VJTF, which includes 5,000 soldiers, in 2014 to ward off the threat of Russian military aggression against the alliance's Baltic members. Living up to its name, it is supposed to be ready to fight within 24 hours, though the new documents show that France and Britain are currently the only major European powers with militaries capable of that kind of response.

But, as Galeotti said, the VJTF is more of a "political trip-wire" than a military force. "The point about this deployment is that it tells Russia: Yes, you might be sending your troops into Poland or Estonia, but you're going to have to kill Germans, and other nationalities, the day you do that," he said. "It's a political commitment to the unity of NATO."

For that reason, he argued, even though the tanks are important, the fact that the Bundeswehr will be sending fewer tanks than it would like to does not necessarily hobble the VJTF's mission. "The Russians are not hell-bent on expansion or invasion. It's not likely, certainly for the foreseeable future, that the Russians will want to tangle with NATO," said Galeotti. "We must remember that European NATO, even without the Americans and the Canadians, has more ground troops than the Russians do."