Though Captain James Cook was certainly not the first person to set foot on Christmas Island—the atoll had been visited by native Pacific Islanders in the past—it was uninhabited when he found it. Both the UK and US later laid claim to the atoll, and they vied for power there for the next 100 years or so, until it gained independence as part of the 33-island Republic of Kiribati and was renamed Kiritimati. Before it gained independence, the US and UK used the atoll as a testing ground for what? Discuss
Source: The Free Dictionary