More than 1100 military personnel from four countries will take part in a training exercise throughout Tararua and Northern Wairarapa.
Residents are being warned to expect to hear helicopters and see armoured vehicles in the districts.
Exercise Alam Halfa has already started in Waiouru with live firing training and is set to move in force to Tararua from Saturday and stay until the end of the month.
The area involved runs from Woodville north to Dannevirke and south down State Highway 2 to Kaiparoro and across to the east coast. Residents are being told they may hear helicopters at night as part of the exercise.
The New Zealand Army and Air Force are being joined on the exercise by US Army, US Marines, Canadian and British Army personnel.
