Relatives of Corporal John Moore, 22, and Private Sean McDonald, 26, spoke of their "devastation" after soldiers described how the pair were killed by an explosion while on patrol in Sangin on Sunday.
The tributes were paid as defence sources said the heavily-trailed Operation Moshtarak was reaching the final "shaping phase" this morning.
British forces are joining Afghan and US allies in rooting out Taliban insurgents from their stronghold in the town of Marjah in Helmand province.
The onslaught will be staged amid calls for defence chiefs to do more to tackle a sharp rise in the number of British troops in Afghanistan suffering from illness and minor injuries.
The National Audit Office said thousands of working days are being lost to potentially preventable less serious complaints like stomach bugs and sprained ankles.
Cpl Moore, from Bellshill, Lanarkshire, and Pte McDonald, who was born in Toronto but went to school in Edinburgh, were "professional, courageous, selfless, and committed - true infantry soldiers", Defence Secretary Bob Ainsworth said.
Cpl Moore, from the Royal Scots Borderers, 1st Battalion The Royal Regiment of Scotland, was commanding his section on a routine night patrol when a roadside bomb detonated, killing him and Pte McDonald.
Mr Ainsworth added: "Hearing about these two brave men, I am filled with admiration for their courage and loyalty."
Cpl Moore's relatives said they were "devastated".
A statement from the family said: "Johnathan was a proud Scottish soldier who was doing a job that he loved - he will be sadly missed by a loving and very proud family. The Army and his family were Johnathan's life we are devastated at our loss."
Pte McDonald, who had a wife, Jennifer, will be "desperately missed", his mother Jacqueline McDonald said.
She added: "My son was so proud to be a soldier. He will be desperately missed by all family and friends. This tragedy has left a hole in our lives and a hole in our heart. Sleep well baby boy."
Cpl Moore, a rising star among his comrades, was a "junior leader of the rarest quality".
Lieutenant Colonel Nick Kitson, commanding officer of 3 Rifles Battle Group, said: "A junior leader of the rarest quality, our Army depends on men like him and his loss is a bitter blow.
"Another of our brightest stars has given his all before we have had the chance to see his full and undoubted potential unfold."
He was "an example to us all", he added.
Lieutenant Colonel Charlie Herbert, of 1st Battalion The Royal Regiment of Scotland, said: "He had all the attributes of the perfect Scottish warrior; bold, charismatic, tough as nails, utterly professional and a born leader of men.
"He was destined for the top; best student on his non-commissioned officer course in 2007, and a star of his corporals course in 2008."
Pte McDonald, who spent much of his time in Afghanistan helping clear improvised explosive devices (IEDs), had also been on three tours of Iraq as well as serving in Bosnia and Northern Ireland.
L/Col Kitson said of him: "In our hierarchical and career focused organisation a 10-year private soldier can be a rarity these days, especially one found on the very frontline, at the tip of the spear as he was.
"Yet such exceptions to the rule are just what bring us true strength and Pte McDonald was certainly no exception in this regard.
"Fearlessly and without hesitation Pte McDonald threw himself at the most dangerous and daunting of tasks that the treacherous alleyways and towering compound walls of eastern Sangin could offer."
L/Col Herbert added: "Like so many of his generation Private Sean McDonald, or Mac as his friends knew him, lived life to the full, pushing himself to the limits, always looking for fun and adventure."
A soldier from 36 Engineer Regiment - part of the counter-IED Task Force - died on Monday, taking the total of British servicemen and women killed since operations in Afghanistan began past that of the Falklands War.
The heavily-trailed Operation Moshtarak is expected to start imminently.
There are currently 30,000 international troops and 10,000 Afghans in Helmand Province.
Mr Ainsworth warned of a "very real risk" that British lives will be lost during the fighting to come, and a senior Army officer yesterday agreed the prospect of casualties "can't be discounted".
Media reports yesterday said 400 troops from the US 5th Stryker Brigade and 250 Afghan soldiers had moved into positions north-east of Marjah, the biggest Taliban-controlled town in the south of the country.
Machine gun fire and rocket-propelled grenades were heard but there were no immediate reports of casualties.
Speaking in London, Prime Minister Gordon Brown said the Afghan-led operation marked an important step in the process of handing over control to local security forces.
Moshtarak would see Afghan forces "clearing, holding and building in the main population centres of their own country", said the PM.
He paid tribute to Britain's armed forces, "their professionalism, their dedication, their expertise, their service and their sacrifice.
"Marjah and a small number of other centres are the last remaining bases for Taliban-led insurgency in the main population areas of Helmand," said Mr Brown.
Mr Ainsworth told the House of Commons Defence Committee that the unusual decision to announce the operation in advance had been taken in part to avoid civilian casualties, which would damage efforts to win the hearts and minds of local people.
Mr Brown, who discussed the offensive with Afghan president Hamid Karzai by telephone at the weekend, said: "Our aim is always to minimise casualties and to separate a hard-line Taliban from those who have been caught up in the insurgency."
Comments