A helicopter is seen during the humanitarian assistance and disaster relief operations at Joint Base Lewis-McChord, southwest of Seattle, Washington state, the United States on Nov. 20, 2015. It was the 3rd time that Chinese and US soldiers engaged in practical field exchange of the kind, as part of an annual bilateral disaster management exchange program aimed at building up capabilities to cooperate in an emergency scenario. In previous two events, the two sides had field exchanges in Oahua, Hawaii, of the US and in Haikou, Hainan of China. (Xinhua/Bao Dandan)

Chinese and American soldiers worked together to practice on humanitarian assistance and disaster relief operations at Joint Base Lewis-McChord, southwest of Seattle, Washington state, the United States on Nov. 20, 2015. It was the 3rd time that Chinese and US soldiers engaged in practical field exchange of the kind, as part of an annual bilateral disaster management exchange program aimed at building up capabilities to cooperate in an emergency scenario. In previous two events, the two sides had field exchanges in Oahua, Hawaii, of the US and in Haikou, Hainan of China. (Xinhua/Bao Dandan)

Chinese and American soldiers worked together to practice on humanitarian assistance and disaster relief operations at Joint Base Lewis-McChord, southwest of Seattle, Washington state, the United States on Nov. 20, 2015. It was the 3rd time that Chinese and US soldiers engaged in practical field exchange of the kind, as part of an annual bilateral disaster management exchange program aimed at building up capabilities to cooperate in an emergency scenario. In previous two events, the two sides had field exchanges in Oahua, Hawaii, of the US and in Haikou, Hainan of China. (Xinhua/Bao Dandan)

Chinese and American soldiers worked together to practice on humanitarian assistance and disaster relief operations at Joint Base Lewis-McChord, southwest of Seattle, Washington state, the United States on Nov. 20, 2015. It was the 3rd time that Chinese and US soldiers engaged in practical field exchange of the kind, as part of an annual bilateral disaster management exchange program aimed at building up capabilities to cooperate in an emergency scenario. In previous two events, the two sides had field exchanges in Oahua, Hawaii, of the US and in Haikou, Hainan of China. (Xinhua/Bao Dandan)

Chinese and American soldiers worked together to practice on humanitarian assistance and disaster relief operations at Joint Base Lewis-McChord, southwest of Seattle, Washington state, the United States on Nov. 20, 2015. It was the 3rd time that Chinese and US soldiers engaged in practical field exchange of the kind, as part of an annual bilateral disaster management exchange program aimed at building up capabilities to cooperate in an emergency scenario. In previous two events, the two sides had field exchanges in Oahua, Hawaii, of the US and in Haikou, Hainan of China. (Xinhua/Bao Dandan)

Chinese and American soldiers worked together to practice on humanitarian assistance and disaster relief operations at Joint Base Lewis-McChord, southwest of Seattle, Washington state, the United States on Nov. 20, 2015. It was the 3rd time that Chinese and US soldiers engaged in practical field exchange of the kind, as part of an annual bilateral disaster management exchange program aimed at building up capabilities to cooperate in an emergency scenario. In previous two events, the two sides had field exchanges in Oahua, Hawaii, of the US and in Haikou, Hainan of China. (Xinhua/Bao Dandan)