Due to North Koreas repeated ballistic missile tests, the US has deemed it viable to begin foot patrols and digging in for any possible armed incursions into South Korea. Due to the fact that North Korea and South Korea are still technically at war, and the strong alliance between the US and South Korea, a North Korean incursion is most likely, but not highly expected.
The US forces are to begin digging fortifications and begin LRRPs (Long Range Recon Patrols) along the DMZ to ensure there aren't any North Korean combatants attempting to cross the DMZ. The North Koreans, will most likely do the same, so expect armed interactions with North Korean foot patrols. Again, remember this is not a state of war, BUT because tensions are so high, war CAN POSSIBLY break out at any given moment, so be prepared at all times, and be wary of your surroundings.