Updated

In the last week, the Taliban have overrun two districts in the north and west of the capital Kabul, temporarily cut a key highway linking the city to the north and staged a suicide bombing targeting government workers — many of whom represented the new, educated generation on whom the hopes for Afghanistan's future are pinned.

Here's a look at some of the factors that have strengthened the radical religious movement:

WHERE DOES THE WAR AGAINST THE TALIBAN STAND?

The U.S. Special Inspector General on Reconstruction in a report earlier this year called the death toll among Afghan National Security Forces in their war against the Taliban "shockingly high." Yet despite the soaring deaths of Afghan soldiers and police, the inspector general said in a separate report that the Taliban now hold sway in nearly 50 percent of the country.

At its peak, the Afghan battlefield involved nearly 150,000 U.S. and NATO soldiers and yet the Taliban remained an undefeated force. Since the drawdown of international troops at the end of 2014, the Afghan military and security forces, with 195,000 soldiers and more than 150,000 police, have struggled to contain the insurgency.

The Taliban have been helped by safe havens in neighboring Pakistan as well as a deeply corrupt government and widespread disillusionment among most Afghans, who have begun to flee the country in unprecedented numbers. Millions live as refugees, mostly in Pakistan and Iran, but they are becoming one of the largest refugee groups seeking safety in Europe.

The war, now in its 16th year, drags on.

WHERE DOES THE TALIBAN'S STRENGTH LIE?

The Taliban's strength has traditionally been in the south and the west of the country predominantly, where ethnic Pashtuns, who make up the backbone of the religious movement, dominate. It is a vast area that borders Pakistan's tribal region, also dominated by ethnic Pashtuns, who in many cases share tribal and family links.

But in recent months the Taliban have waged blistering assaults in the north and the west, with success in Ghor and Faryab provinces. Although pockets of ethnic Pashtuns live in these areas, analysts say their increasing presence and pressure reflects the weakness of the Afghan National Security Forces to repel Taliban assaults. Previously, the Taliban were satisfied to control areas outside the heavily fortified centers, where government administrators operate and rarely venture beyond. But increasingly they are setting their sites on taking over district centers, forcing government and military personnel to withdraw.

In southern Helmand province, the Taliban overran Sangin district, which was defended by Afghan National Security Forces with support from NATO and U.S. forces. Most analysts and residents say 80 percent of Helmand, prized by both the Taliban and corrupt government officials for its vast opium fields, has largely been under Taliban control since 2004. Until now, however, the centers had remained with the government.

WHAT FACTORS IN AFGHANISTAN GIVE STRENGTH TO THE TALIBAN?

After 16 years and billions of dollars in international investment, widespread corruption in the government and its inability to deliver justice, security and services outside of its centers has left the vast majority of Afghans disillusioned, resentful of their government and unwilling to risk Taliban payback by siding with the government or its security forces.

In Pashtun dominated areas, the Taliban are often seen as a better alternative to corrupt administrators and police. Most turn to the Taliban to settle disputes and avoid paying bribes and payoffs to police and government. The Afghan National Security Forces are poorly trained as the international community rushed to get Afghan troops and police on the ground. A senior police official speaking on condition of anonymity fearing government retaliation said in more remote areas of the country, Afghan troops are poorly supplied, even with basic foodstuff. Their equipment is often second rate and the coordination between Afghan army, national police and local police is non-existent. In many areas the relationship is hostile.

The police official said corruption has resulted in the large-scale sale of military equipment.

Security analyst Sayed Fazlullah Wahidi, former governor of eastern Kunar province and western Herat province, says "corruption, the lack of leadership, it all creates an easy environment for the Taliban to flourish."

WHAT FACTORS OUTSIDE OF AFGHANISTAN GIVE STRENGTH TO THE TALIBAN?

Pakistan is blamed for fomenting violence in Afghanistan, giving aid to the Taliban and providing them with safe havens from which they are able to regroup and return to the Afghan battlefield. Pakistan denies the allegations, but even its highest ranking foreign affairs official, Sartaj Aziz, acknowledged Taliban groups have been living in Pakistan on and off for 30 years.

It is their historic links to Pakistan's army and its powerful intelligence agency, the ISI, that both Afghanistan and the United States says gives the Taliban its strength. It is these same links that both Washington and Kabul want Pakistan to use to press the Taliban into peace negotiations.

Pakistan says its influence is overstated, yet its leverage is significant. Taliban leaders live in Pakistan's cities, run businesses and send their children to local schools.

Pakistan has long seen ethnic Pashtuns in Afghanistan as necessary allies because of its own tribal areas and two border provinces dominated by ethnic Pashtuns. But post 9-11, increasingly Pakistan has viewed the Afghan government as an ally of its enemy India, against whom it has fought and lost three wars.

Afghanistan has long demanded Pakistan be punished for harboring and aiding Taliban fighters. Yet the senior police official says Pakistan is no longer its only headache, nor is it the only nation aiding the Taliban. He says the Taliban receive aid from both from Iran and Russia, an allegation both countries also deny.

Political leader and former minister, Anwarul Haq Ahahdi said "at one time it was just Pakistan you had to worry about, now it is Iran involved and Russia involved. It is more difficult today. We are in a very difficult situation."