The fire on Saddleworth Moor could rage on for "weeks," says Greater Manchester Fire and Rescue service.
About 100 soldiers and an RAF Chinook helicopter are due to arrive this morning (June 28) to help tackle the blaze.
The troops from the 4th Battalion, Royal Regiment of Scotland, were being sent overnight to join firefighters across Tameside, on the edge of the moor.
Some 55 firefighters were still trying to quell multiple pockets of flames spanning up to 3.7 miles (6km) on Wednesday night.
The soldiers were heading from their barracks in Catterick and will operate out of an Army training centre to control the fire by managing water lines and fire beating, among other means of support.
"We can see this being prolonged for days if not weeks," said Tony Hunter, head of prevention at Greater Manchester Fire and Rescue.
Troops protecting the UK
Defence Secretary Gavin Williamson said it is a display of British troops protecting the UK "no matter the time, no matter the place, and no matter the problem".
The troops were answering a call for assistance from Greater Manchester Fire and Rescue Service (GMFRS).
The Chinook, which will fly out of RAF Odiham, Hampshire, on Thursday morning, will move high-volume pump equipment by air to help douse the flames in difficult to access areas.
Dave Keelan, director of emergency response at GMFRS, had also suggested it could be used to transport firefighters.
He said firefighters were working "extremely hard in really hot conditions" but morale was high, adding: "It's more of a task to get them down here to rest."
34 households evacuated
Problems faced included frequent changes in wind direction, the peat-embedded terrain which requires large quantities of water to extinguish flames and the searing temperatures.
As of Wednesday lunchtime there were seven separate fire incidents ongoing on areas of the moors, including Calico Crescent, Intake Cottage, Intake Lane, Caste Farm, Dovestones, Higher Swineshaw and Chew Road.
Some 34 households were evacuated in Calico Crescent in the village of Carrbrook, Stalybridge, on Tuesday night but residents were allowed to return after air quality assessments.
Air quality levels in the area are being monitored regularly in different locations with people in affected areas urged to follow advice from Public Health England and keep their windows and doors closed.
No rain is forecast for Tameside for the rest of the week at least.