The United States and the Taliban signed a peace deal Saturday that marks a turning point in Afghanistan’s more than 18-year war. The United States invaded Afghanistan in the wake of the Sept. 11, 2001, attacks that were planned from Afghan territory. The conflict has killed tens of thousands and cost more than $2 trillion.

Here is what you need know:

U.S. troop withdrawals

The deal states that all U.S. troops will be withdrawn from Afghanistan within 14 months if the Taliban upholds specific commitments. This was not a widely anticipated aspect of the peace deal. While the U.S. military command in Kabul already began drawing down troops in Afghanistan, it was expected that a small counterterrorism force would be left behind.

There are currently about 12,000 U.S. troops in Afghanistan, and the first phase of this full withdrawal would bring those numbers down to 8,600 troops within 135 days. During that time, U.S. allies and coalition members will also proportionally draw down their forces.

Then, over the next nearly 10 months, the rest of the U.S. troops would be withdrawn as long as the Taliban upholds its end of the bargain. Broadly, that means the group pledges to engage in talks with the Afghan government and commits not to allow terrorist groups to use Afghan soil to plot attacks against the United States or its allies.

Obstacles to peace

Many challenges remain. The diplomatic effort to get the United States and the Taliban to agree to a deal took years. It is not unreasonable to assume talks between the Afghan government and the Taliban could be a similarly lengthy effort.

The Taliban has already suggested their commitments not to harbor terrorist groups come with caveats. While the Taliban has played a large role in the fight against the Islamic State in Afghanistan, the group still maintains ties to al-Qaeda.

Also, Afghanistan is riddled with armed groups that do not want to see a peace deal between the United States and the Taliban. Some of these armed groups are not aligned with either the government or the Taliban. A peace deal will not necessarily halt their attacks.

In addition, decades of conflict in Afghanistan have created space for profitable smuggling routes and a growing narcotics trade. Peace could make it more difficult for these illicit activities to continue, and it would not be surprising for these groups to turn to violence to protect their financial interests.

Can relative calm remain?

A week-long reduction in violence countrywide in Afghanistan was described by U.S. negotiators as a key precondition to the signing of a peace deal. But it is unclear what will happen to violence levels in Afghanistan next.

Over the past week, levels of violence decreased about 80 percent in both urban and rural parts of the country. Afghan government forces and Taliban fighters felt safe enough to approach one another, moves unthinkable just over a week ago.

U.S. officials have said they hope violence will remain low throughout the intra-Afghan talks.

But following the signing of the deal Saturday, the spokesman for the Taliban’s Qatar office, Suhail Shaheen, told The Washington Post the reduction in violence agreement was no longer in effect. “That was for making the environment conducive to sign the deal,” he said.

The Taliban hopes to achieve a “permanent solution” to violence levels in Afghanistan, he added. “But right now [there is] no such understanding of a cease-fire or reduction in violence.”

Prisoner swap

Prisoner swaps have been a controversial aspect of peace negotiations with the United States. Taliban prisoners are key leverage for the Afghan government, and Kabul has long said it would not release prisoners until after intra-Afghan talks.

But the deal signed Saturday states that 5,000 prisoners Taliban are to be released by the date that intra-Afghan talks are required to start: March 10. The Taliban has long made this a key demand.

It is unclear how this will impact intra-Afghan talks. The Afghan government is left with essentially very little bargaining power, as the United States has committed to withdrawing all its troops and has stipulated the prisoner swap occur before negotiations begin between the Afghan government and the Taliban.

What’s next for talks?

The Afghan government needs to assemble a negotiating team. But that could be an even more complicated task at the moment, as the country is in the midst of a deepening political crisis.

Disputed election results were announced in mid-February, and both President Ashraf Ghani and his main rival have declared victory. Ghani’s rival has begun forcibly replacing governors in the north of the country and is threatening to set up a parallel government.

All of this has left Kabul deeply divided and has the potential to undermine Ghani’s mandate to form an inclusive team to negotiate with the Taliban.