Apple CEO Tim Cook arrived in Hanoi, Vietnam, on Monday as the company looks to boost sales in new markets and diversify its supply chain. Vietnam is one of Apple's most important manufacturing hubs, with Apple becoming the country's third-largest smartphone vendor behind Oppo and Samsung. Vietnam is a key location for Apple's assembly of products beyond iPhones like the MacBook, iPad, and Apple Watch. The visit comes as Apple faces falling iPhone shipments and intense competition in high-end markets like China.