About 80 firefighters worked through the night to tackle a new grass fire on Winter Hill, near Rivington, around 30 miles (50km) from the large blaze on Saddleworth Moor.
Greater Manchester Fire and Rescue Service (GMFRS) said the eruption of a third blaze at Higher Swineshaw from 4am, along with that on the moor covering around seven square miles, meant they were “massively busy”.
Scottish soldiers from the 100-strong A Company of the 4th Battalion, Royal Regiment of Scotland, known as the Highlanders, have joined more than 100 firefighters who have been battling the blaze since Sunday.
Major Phil Morgan, commanding the army detachment, said: “We meet every challenge and commit 100% in what we do.
“Currently we have broken our boys down into various locations and we are beating the fire with paddles. We are supporting them by moving equipment, we are putting water on the fires and we are doing everything we can to stop this fire at the moment.”
Tony Hunter, assistant chief fire officer of GMFRS, said there had been a “significant effect” on the blaze in the past 24 hours.
“We have made significant improvements but I would put an air of caution there, though. We had a similar occasion yesterday where we thought we were on top of it and it flared up.”
Mr Hunter warned that while the fire was now “contained and under control”, “things can develop” and if the wind blows the flames back on to the moors it will act as a “fuel source” for the fire.
He said the operation could last for weeks before the fire burns itself out.
The army deployment is for an initial 48 hours.
Mr Hunter said a “significant downpour of rain” would help – but none is forecast for days as the heatwave continues.
Pete Woodward, whose home backs on to the hills just 20 metres away, spent the night at his brother’s home nearby after being evacuated on Tuesday evening.
He said: “I got back to the house last night to a towering inferno behind, very apocalyptic in view, and it was quite scary but exciting at the same time.”
Dave Saxon, director of operations at Tameside Council, said the authority was monitoring air quality, which had improved on Thursday, and that there had been no increase in GP appointments or attendance at A&E.
Fire chiefs have said they are “not confident” of finding out how the fire began, given the size of the blaze, and there is no evidence it was started by barbecues or off-road bikers.
Meanwhile, the UK enjoyed the hottest day of the year on Thursday as the temperature soared to 33C (91.4F).
Porthmadog in Wales reached the sweltering high, beating successive highs since Monday.
The hot weather is expected to continue into the weekend.