Days prior to the revelation that a new port which could be used by the US Marines was being planned on the edge of Darwin, a placard popped up on one of the city's main commuter arteries.

"No USA war base" blared the letters of the sign hanging off the Bagot Road pedestrian bridge, which neighbours land owned by Australia's Defence Department.

Other similarly slapdash carboard banners were also erected along the street.

Their appearance signalled that some within the tropical capital may have been aware of the impending news — and perhaps the rest of the region's residents shouldn't have been too surprised.

While nothing has yet been declared through official government or Defence channels, the signs of such a development have long existed.

Whether or not the NT will see more foreign boots on the ground, the ADF has been steadily improving and upgrading defence infrastructure in and around Darwin in recent years — a fact which falls somewhat contradictory to the reality that ADF numbers have been on a steady decline in Darwin for the past decade.