Over the past year, the Pentagon has talked a lot about refocusing on an era of "great power competition", moving from a focus on Iraqi and Afghan-style counterinsurgency to countering China and Russia.

Throughout March, the U.S. military was showing what that really means.

U.S. soldiers were arriving in Germany to pick up tanks and armored vehicles stored in Europe before heading to Poland for exercises. Earlier, hundreds of U.S. Marines from the 31st Marine Expedition Unit flew 965 km in a training exercise for seizing a small Japanese island, and set up artillery and an airbase to then conduct further strikes and troop movements. It was a high-profile demonstration of a tactic known as "island hopping" that was first honed against Japan in World War II and is now seen by the United States as key to any future war with China.