It is the Taliban's biggest success since 2001: International observers are unanimous. They have interpreted the attack on Kunduz as a clear sign of the Islamist rebel group's strength. On Monday, Afghan forces surrendered the northern city to Taliban guerrillas and have been unable to take it back since.

Kunduz is key

Kunduz, with its 300,000 residents, is strategically important, and not just for Afghanistan. Whoever controls the city can push into further parts of northern Afghanistan. In neighboring Takhar Province, several attacks on police and army facilities have already been registered.

Beyond that, Kunduz lies on an important road connecting Kabul to neighboring northern states. "Taliban control of such an important transportation route represents a significant interruption of logistics for the Afghan armed forces, and also gives the Taliban direct access to smuggling routes to Tajikistan and Uzbekistan," says Jason Campbell, security expert from the RAND corporation, a think tank, in an interview with DW.

Instability next door

From Kunduz, it is only about 70 kilometers (44 miles) to Tajikistan. Kunduz played an important role in the Tajik civil war which claimed the lives of almost 150,000 people back in the 1990s - this was even more important than the role it has played in the war that has been going on in Afghanistan since 2001. Kunduz was the Tajikistan Islamic opposition's most important safe haven. And the city could well regain that role should the situation in Tajikistan escalate once again. Things are anything but stable in the neighboring country today.

On September 29, the Supreme Court of the Republic of Tajikistan prohibited the "Islamic Renaissance Party of Tajikistan." The decision was followed by the arrest of dozens of key party members. Party chair Muhiddin Kabiri fled to Turkey this spring. The Islamist party is considered moderate and was the most important voice of the opposition. Now the party has been banned from the public square, which has led to the development of local power structures and in some cases is even leading to authoritarian structures similar to those in Turkmenistan, says the Russian political scientist and Central Asia expert, Andrei Serenko.

But the Tajik authoritarian model is defined by repetitive episodes of excessive violence. In early September, President Emomali Rahmon, who has run the country singlehandedly for the past 20 years, sent government forces into a pitched gun battle with fugitive Deputy Defense Minister Abduhalim Nazarzoda. It lasted several days. In May, another high-ranking Tajik officer fled to Syria to fight with the terror militia "Islamic State" (IS). Beyond that, several opposition politicians were sentenced to long prison sentences in 2015. The country remains one of the poorest in the world. Unemployment has also risen sharply in Tajikistan as a result of the Russian financial crisis, with many working migrants returning home from Russia and flooding the Tajik job market.

Who controls the border?

Matters are made even worse by the fact that the Afghan-Tajik border is likely rather porous. On September 24, members of the "Islamic Jihad Union" (IJU), known in Germany through the so-called "Sauerland Group" that had conspired to carry out attacks at Frankfurt Airport and Ramstein Air Base, claimed to control large sections of the border in a posting on their website. As proof, they uploaded photos of themselves - armed with guns - crossing the Amu Darya river on the Afghan-Tajik border.

The claims could not be verified through other sources. Nonetheless, it is known that terror organizations stemming from Central Asia, such as IJU or the "Islamic Movement of Uzbekistan," have built up strongholds near Kunduz, says Michael Kugelman, Afghanistan expert at the Woodrow Wilson International Center for Scholars. Pakistani political expert Ahmed Rashid says he believes that as many as 5,000 armed militants from Central Asia are fighting alongside the Taliban in northern Afghanistan.