The United States and the Taliban signed an agreement aimed at ending the eighteen-year war in Afghanistan, but many factors could still disrupt the peace process.

For many policymakers, economic sanctions have become the tool of choice to respond to major geopolitical challenges such as terrorism and conflict.

Relations between the two countries, long bound by common interests in oil and security, have strained over what some analysts see as a more assertive Saudi foreign policy.

Charges of foreign power interference in the U.S. presidential election have raised grave national security concerns and touched off multiple federal inquiries that could drag on for months.