Snowden enlisted in the army in 2004 and was later sent to the battlefield in Iraq. Unfortunately, he injured his legs during training. After retiring, Snowden returned to the United States and applied to join the CIA. After that, he joined the National Security Agency and accidentally discovered that the government had implemented a large-scale surveillance plan on citizens' phones and social networks after the "9.11" incident, so he leaked a large number of confidential documents. After the incident, Snowden was wanted by the authorities and fled to Hong Kong. After that, he fled to Russia to seek asylum.