The United States (U.S.) military withdrawal from Afghanistan in August 2021 was met with turmoil as Taliban regained control of most of the country, including Kabul. These events have affected many and were widely discussed on social media, especially in the U.S. In this work, we focus on Twitter discourse regarding these events, especially potential opinion shifts over time and the effect social media posts by established U.S. legislators might have had on online public perception. To this end, we investigate two datasets on the war in Afghanistan, consisting of Twitter posts by self-identified U.S. accounts and conversation threads initiated by U.S. politicians. We find that Twitter users' discussions revolve around the Kabul airport event, President Biden's handling of the situation, and people affected by the U.S. withdrawal. Microframe analysis indicates that discourse centers the humanitarianism underlying these occurrences and politically leans liberal, focusing on care and fairness. Lastly, network analysis shows that Republicans are far more active on Twitter compared to Democrats and there is more positive sentiment than negative in their conversations. / Master of Science / The United States (U.S.) military withdrawal from Afghanistan in August 2021 was met with turmoil as Taliban regained control of most of the country, including Kabul. These events have affected many and were widely discussed on social media, especially in the U.S. In this work, we focus on Twitter regarding these events, and study if public's opinion change over time especially by the posts of legislators. Therefore, we used two datasets about unrest in Afghanistan after the Taliban takeover. One datasets consists of of Twitter posts by self-identified U.S. accounts and the other one are the conversation threads initiated by U.S. politicians. We find that Twitter users' discussions revolve around the Kabul airport event, President Biden's handling of the situation, and people affected by the U.S. withdrawal. According to our findings based on several methods analyzing the content of the posts of Twitter users, the pressing issues are the humanitarian concerns for the people who could be the target of Taliban. Last but not least, we also studied the relationship between legislators and twitter users along with the dominant sentiment about the topic. Our analysis shows that Republicans are far more active on Twitter compare to Democrats and there is more positive sentiment than negative in their conversations.