When the army loses one senior officer to resignation it may be regarded as a misfortune but to lose two looks like carelessness.

That was the feeling which coursed through the army’s higher command on Friday when it was announced that Major-General Andrew Mackay, one of the army’s best-respected soldiers, had decided to stand down as the commander of the 2nd Division, the formation responsible for army matters in Scotland, Ireland and the north of England.

Mackay’s decision follows almost a year after Brigadier Ed Butler, another high-value commander, did much the same thing when he too decided to send in his papers and head back to civvy street. There is a connection. Both men commanded infantry brigades in Helmand Province and both have criticised the direction of operations in Afghanistan. Both, too, are motivated and highly principled soldiers whose opinions are respected and who care deeply about the men and women under their command. Butler commanded 16 Air Assault brigade in 2006 and Mackay commanded 52 Infantry Brigade in the same role a year later.

Coming on top of other untimely incidents such as the recent standing down of General Sir Richard Dannatt, Chief of the General Staff, and the early resignations of younger officers such as Major Nick Haston, Mackay’s deputy chief of staff, and Lieutenant-Colonel Stuart Tootal who commanded 3rd Parachute Regiment in Afghanistan there is a growing feeling in military circles that there is a gulf between those who execute the operations in Helmand and the politicians who sanction them.

“This succession of senior resignation is obviously not good news for the army at a time when questions are being asked about our presence in Afghanistan,” says a senior army officer with experience of operations in Helmand. “We’re all aware of the stresses and while some things have improved we’re not really in a full-on war footing.”

In the wake of Mackay’s decision, which came as a great shock even to closest colleagues, the Ministry of Defence insisted that he had resigned “for personal reasons” and no mention was made of any disagreement over policy. On one level that is probably true. A soldier with a lifetime of service to the British Army would hardly take such a decision lightly and according to those close to Mackay there was a good deal of agonising before he decided to tell General Sir David Richards, the new Chief of the General Staff and head of the army, that he had decided to resign his commission.

“I’d be assuming that frustration over issues in Afghanistan would be part of the issue,” said Major Nick Haston in an interview with BBC Radio 4’s World at One programme. “I would be guessing, but I would assume there’d also be other issues such as the general funding problems in the military just now.”

According to others who served with Mackay in Helmand in 2007 there is much more to the decision than a personal desire to quit a job he clearly loved and to do other things. Within hours of the announcement the army’s rumour mill was awash with stories that Mackay was deeply disillusioned with current policy in Afghanistan and that he had reached the end of his tether as far as his frustrations were concerned. He is also thought to be angered by proposed changes in the army’s divisional structure which will see a reduction in the army’s “foot print” in Scotland.

“Only General Andrew [sic] can say precisely why he chose to resign so soon into his latest command but a man like him would have deep-seated reasons,” says another officer who knows the general. “It’s been clear from comments that he has made in public as well as in private that he’s unhappy with the absence of political grip.”

That certainly rings true because Mackay has form on that score. In 2007 he commanded 52 Infantry Brigade during a six month tour of duty in Helmand Province and on arriving he admitted to be being shocked by the fact that his predecessors were “making it up as we go along” and that there was no coherent counter-insurgency policy in place to take on and defeat the Taliban. He followed this up with some harsh words about the failure of the battle to win hearts and minds, claiming in March this year that through the army’s inability to gain the support of the local population “one of the central tenets of counter-insurgency doctrine is failing”.

Mackay has also been fearless in criticising the level of equipment which his men had to use and has been unafraid to make his views known to others. In Operation Snakebite, the history of the 2007 deployment author Stephen Gray published a confidential memo in which Mackay admitted that much of the equipment available to his brigade was “tired, limited and failing regularly”. More recently Mackay has told friends that he fears the consequences for troop morale if the government fails to make clear its policy in Afghanistan.

Whatever else, his resignation comes at a bad time for the government when popular support for the war in Afghanistan is waning and questions are being asked by the commitment to the fighting in Helmand. There has been a spike in casualties, one of the latest being Acting Sergeant Michael Lockett, 2nd Mercian Regiment, who had already won a Military Cross and was nearing the end of his tour of duty when he was killed by a roadside bomb. Earlier this month former army officer Eric Joyce MP resigned as a parliamentary private secretary over perceived failures in the government’s policy and there has been the accumulation of resignations of senior officers.

Then, on the same day that Mackay’s resignation was announced a new book, No Expenses Spared, revealed that workers who processed MPs’ expenses claims included serving soldiers, who were moonlighting between tours of duty in Iraq and Afghanistan to earn extra cash for body armour and other vital equipment. Enraged by the disparity between the MPs’ claims and the lack of money available for the army in Afghanistan they decided to go public on the matter.

Very much an “educated soldier” with a reputation for thinking things through, Mackay began his career in the Royal Hong Kong Police before being commissioned in 1st King’s Own Scottish Borderers which he commanded between 1988 and 1990. A graduate of the army’s staff college, he spent three years in the strategic planning group at Supreme Headquarters Allied Powers Europe, where he was responsible for the strategic and operational planning in the Balkans. Earlier this year following his successful tour of Helmand, for which he was appointed CBE, he was promoted to the rank of major-general in charge of 2nd Division at Craigiehall outside Edinburgh.

However, it is in the field of counter-insurgency doctrine that he came to the fore during the Helmand deployment. Events in Iraq in the aftermath of the invasion in 2003 had shown that the British Army’s ability to defeat terrorists had deteriorated. Too much emphasis was placed on the experience of Northern Ireland and there was a need, as he put it, to produce “a different approach and ingenuity in facing the daily challenges that complex counter-insurgencies create.” Above all, he insisted that killing the opposition was not the only indicator of success - body counts counted for nothing unless those outside the battle were being protected and offered support.

“Unless we retain, gain and win the consent of the population within Helmand, we lose the campaign,” he argued. “The population is the prize.”

His theories were not always popular but they did win him friends in the US Army. General David Petraeus, the architect of the surge in Baghdad and the senior land forces commander, was a friend and admirer who jokingly referred to Mackay in a recent lecture on counter-insurgency warfare as the “King of Scotland”. Last month he was Mackay’s guest at the Edinburgh Military Tattoo.

Inevitably, perhaps, there have been criticisms within the army that Mackay should have stood his ground and continued fighting for his soldiers while still wearing uniform. That would be to misunderstand the motivation of a very principled soldier who clearly decided one way or another, that enough was enough and that there was no more wriggle room for him to cope with his frustrations. As he explains in his new doctrine on counter-insurgency policy - the legacy he leaves the army - it is axiomatic that soldiers will never have enough of everything they need.

“This is not because provision is consistently tardy, held up or unavailable (although there are frequent examples when this does happen); it is largely because the degree of expectation relative to progress being made is high. And so it should be. I have concluded that success in managing counter-insurgency is often less to do with getting what you want but wanting what you’ve got.”