On Friday, at the Port of Napier, the Americans will be landing.
A US Army contingent of about 85 troops, medical support staff and military police, will step ashore from the logistics ship HMNZS Canterbury which is due to arrive in port about 8am.
The American troops will be joining about 1400 New Zealand army, navy and air force personnel taking part in Exercise Alarm Halfa - one of the biggest combined forces exercises to be staged across the Hawke's Bay region in more than a decade.
Defence communications advisor Paul Stein said the 10-day exercise had been five months in the planning, and would see troops movements by land, sea and air into the region.
About 35 US Marines were also in the country and they too would be involved in the exercise - spread throughout Kiwi units.
The Canterbury, as well as carrying a large contingent of troops from the South Island, would also be unloading a fleet of LAVs (light armoured vehicles).
The movements of the troops, and their initial destinations, were not completely set in a time schedule as the exercise was designed to test units with a diverse series of "incidents".
"There will be objectives emerging along the way," Mr Stein said.
"This will be a very mobile army."
The exercise scenario is effectively based on restoring stability to a small nation which is seeking self-governance.
"But there are insurgent elements at work."
It was a scenario that had been played out, in reality, in several spots round the world, Mr Stein said. Some troop groups would head for the Roy's Hill region near Hastings to set up camp, while others would be marching north.
"We have had excellent co-operation from rural landowners in the area."
Battle exercises including raids and rescues would be taking place, and explosives and gunfire would be heard in some country areas - although neighbouring property holders had been notified.
The RNZAF's 3 Squadron of helicopters will be based at Bridge Pa Aerodrome from Friday through to Monday, while HMNZS Canterbury will be in port until May 1.