Over the next four years, approximately 30,000 Marines and their families will move to the small island of Guam, nearly tripling its presence there.

It's part of a larger agreement that the U.S. signed with Japan to realign American forces in the Pacific, but how will this multi-billion dollar move impact the lives and lifestyle of Guam's nearly 200,000 residents?

This week, NOW on PBS travels to the U.S. territory of Guam to find out whether their environment and infrastructure can support such a large and quick infusion of people, and why the buildup is vital to our national security.