The United States Department of Veterans Affairs – VA, as it's known – is a colossal organisation dedicated to the welfare of veterans and their families. Its budget for 2017 is $180 billion – around £141bn. Congress established the Veterans Bureau in 1921, combining three federal agencies. Warren Harding, the new president, installed an old friend, Charles Forbes, as its head.

But Forbes was the wrong man for the job. He and his hangers-on bled the bureau dry on an industrial level. Eventually, he was charged with conspiring to defraud the US government and jailed for two years but not before a furious Harding had gripped him by the throat and screamed: "You yellow rat! You double-crossing bastard."

Forbes is part of the dark gallery of expat Scots – crooks, conmen, murderers – in a book by Iain Lundy, himself an expat in the US, a former journalist at The Herald's sister paper, the Evening Times. The book is called Between Daylight and Hell: Scots Who Left a Stain on American History.

In his introduction Lundy writes that Scots have done everything in the US. One man helped build the Statue of Liberty, another saved the buffalo from extinction. In addition, the ranks of celebrated Scots include the Dunfermline-born industrialist Andrew Carnegie, and John Muir, the man from Dunbar who became the father of the modern conservation movement.

At the opposite end of the scale was Forbes, slippery as an eel and possessed of few redeeming qualities. He was, says Lundy, "a shyster and a conman, a swindler and a two-bit huckster, a playboy and a cheating womaniser, an army deserter and a jailbird".

Forbes was born in 1877, in Glenluce, Wigtownshire. By 1900 the Forbes family was listed in the US Census as living in Massachusetts. Forbes enjoyed an expensive education, at the Massachusetts Institute of Technology among other places.

He joined the army and served in the Philippines, and afterwards became a civil engineer and a well-known figure in Democratic Party circles. He helped expand the US naval station at Pearl Harbor, and it was in Hawaii that he became firm friends with Harding, then a senator.

During the Great War he saw service in France as a signalman with the 33rd Infantry Division, American Expeditionary Forces. He ended up as a lieutenant-colonel and earned both the Distinguished Service Medal and the Croix de Guerre.

Harding became president in 1921 and when it came to appointing the first head of the Veterans Bureau, he looked no further than his old friend Forbes, who was already running the War Risk Insurance Bureau, one of the agencies that were merged to form the bureau. This was one of the many examples of cronyism that tainted Harding's administration.

Forbes established a network of 14 regional Veterans Bureau offices and put many old friends in charge of the 30,000 employees. Some travelled from coast to coast ostensibly in search of possible sites for new hospitals but instead staged drunken parties at public expense.

What followed was, as one historian put it, tantamount to Forbes establishing an "opportunistic patchwork of individual bribery and greed". According to Lundy, Forbes "was up to his neck in dizzying levels of corruption, promising private construction firms land and building contracts in exchange for kickbacks worth thousands of dollars ... Heavy drinking parties, all on Bureau expenses, became the norm. Forbes even boasted that he would soon be promoted to the president’s cabinet where more ‘opportunities’ would present themselves."

In 1922 Forbes received $5,000 in cash from a construction boss, who then received hospital contracts. Forbes in turn received thousands of dollars plus a percentage of the company’s profits on the deal. He also sold nearly $7m of surplus medical equipment to private interests for $600,000.

While all of this was going on, the veterans – the very people the bureau was designed to help – were virtually ignored. More than 300,000 US soldiers had been wounded in combat during the First World War but only 47,000 of them had their claims for disability insurance approved. Thousands had their applications rejected. Forbes had even failed to open 200,000 pieces of veterans' mail received by his office. As a newspaper columnist later wrote, "Congress little realizes that its creature, the Veterans Bureau, has probably made wrecks of more men since the war than the war itself took in dead and maimed."

But Forbes failed to cover his tracks, and he had made too many enemies for his spree to last. Harding at last got wise to his friend's misdeeds, and Forbes resigned on February 15, 1923. Harding, whose time in office had been dogged by scandal, died that August, three years before his 60th birthday.

Forbes served one year and eight months of his jail sentence. He died in 1952. Despite having callously ignored the pleadings of thousands of veterans, and pocketing money earmarked for their recuperation, he was granted a burial plot at Arlington National Cemetery, the most hallowed ground in the United States.

The recent presidential battle between Donald Trump and Hillary Clinton was unedifying in so many ways, largely to Trump's inflammatory rhetoric – but it was child's play compared with the contest that took place in 1800 between John Adams, the Federalist incumbent, and his Republican challenger, Vice-President Thomas Jefferson.

It was a campaign of bitter mudslinging but it plumbed a new depth when one anonymously-written pamphlet, The Prospect Before Us, asserted that Adams was not merely "mentally deranged" but also "a hideous hermaphroditical character who has neither the force and firmness of a man nor the gentleness and sensibility of a woman".

This understandably enraged Adams and his wife, Abigail. The president reached for his highly controversial Sedition Act in order to punish the author, a political pamphleteer and journalist by the name of James Thomson Callender. Callender – "Jefferson’s personal attack dog, the future president’s ‘hired pen’", says Lundy – was convicted of sedition and jailed for nine months. Jefferson, however, won the presidential election, and his first act was to pardon and release Callender and a number of other writers who had suffered the same fate.

Callender was born in 1758 and spent his childhood in Edinburgh, Stirling or the Borders. He made his name in his native land with pamphlets that savaged Samuel Johnson, the Excise Service and Britain's empire building, before setting sail for America in 1793.

This was a boom decade for newspapers and political pamphlets in the States. There were publications in every city, town and village, and readership numbers exploded. Editors, buoyed by the freedom of speech clause in the US Constitution’s First Amendment, were fearless, and began printing opinions in sensational terms.

Callender flourished in such an atmosphere. He wrote an article attacking the revered George Washington, and in a 1797 pamphlet he sensationally revealed the sexual relationship between Alexander Hamilton, another of the key Founding Fathers, and a married woman, and the blackmail that had resulted.

Bankrolled by Jefferson, he became editor of the Richmond Examiner, a Virginia newspaper, turning it into a Republican scandal-sheet and maintaining his fierce anti-Adams rhetoric. But he later turned against Jefferson, and claimed in 1802 that Jefferson had fathered children with his slave, Sally Hemings. It was an allegation that a later historian would describe as Callender’s "literary weapon of mass destruction against the president".

Virginia society closed ranks against Callender, and even his Federalist newspaper allies distanced themselves. In 1803 he was jailed a second time. Ten days after his release, he was seen in a state of extreme intoxication in the streets of Richmond. The following day his body was recovered from the James River. Some said he had fallen into three feet of water and been too drunk to get back up. Others suggested he had committed suicide.

Concludes Lundy: "The Founding Fathers Callender vilified wrote a nation’s Constitution that is followed more than 300 years later. Every American can quote from it. The bitter vitriol that spilled from Callender’s pen has largely faded into obscurity. Yet the trash journalism that he perfected persists."

Of William Cameron Stewart it was once said that "he seemed to be filled with an insane desire to slaughter as many as possible, and he hewed them down without the least mercy." The fact that Stewart, a Scot, was a Mormon, and that the words were uttered by a fellow member of the church, is just one of the arresting facts of his story.

Stewart, who spent part of his childhood in Lochaber, became a Mormon convert and in 1853 he sailed from Liverpool to New Orleans then headed for Iowa. There, he joined tens of thousands of Mormon pioneers on their long westward trek.

In September 1857 a notorious massacre took place at Mountain Meadows, in southern Utah. Lundy writes: "At least 120 emigrants on a west-bound wagon train were lured to their deaths by members of a Mormon militia. These members were armed to the teeth, and many had their faces painted to make them look like Indians.

"[Stewart's] actions during the killing were animalistic in their brutality. He went on a sadistic and feral rampage that stands comparison with any American outlaw. Stewart showed his victims not a single ounce of mercy, even as they pleaded for their lives. Of all those who participated in the butchering of the defenceless homesteaders, multiple witnesses described him as the most bloodthirsty."

Behind the mass killings lay a grim blend of hysteria, revenge, hatred and fear born out of the belief that the Church of Latter-Day Saints, an institution that was only 27 years old at this time, was under attack from mainstream America. Lundy's book chronicles the birth of the church in 1830, and the fact America "was quite simply not ready to embrace such a profound alternative to its long-standing spiritual beliefs". In Missouri, the church was persecuted but armed Mormons retaliated. Seventeen Mormons were killed by a militia unit after the state's governor ordered that Mormons be "exterminated or driven from the state". After considerable further bloodshed the Mormons trekked 1,200 miles to set up home in Utah's Great Salt Basin.

By 1857, however, Arkansas, Missouri, Illinois and Ohio all featured on the Mormon tablet of revenge: woe betide anyone from these states who dared cross Mormon territory. Other factors contributed to the massacre. There was a siege mentality among the church community. President James Buchanan ordered the army to march on Utah in response to the hostility his officials were receiving.

The wagon-train of emigrants happened to come from north-west Arkansas, one of the "enemy" states. Rumours were spread. The atmosphere became fevered. The emigrants were not to know they were heading to their deaths.

Members of the Paiute tribe began the massacre but suffered numerous losses, and many of the survivors found they no longer had an appetite for bloodshed. Without hesitation, the Mormon civic, religious and military leaders in Cedar City decided to finish matters. With a small band of Paiute still onside by Friday, September 11, a number of Mormons readied for the action, with their faces painted like tribesmen's.

The elimination plan, says Lundy, was cool, clinical, brutal and stomach-churning in its savagery. The Mormons were to promise the emigrants safe passage through the Meadows then, at a given signal, kill every man, woman and child, except those too young to remember.

The book details the massacre, and Stewart's relentlessly grim role. "It was a well-orchestrated and calculated slaughter perpetrated by armed militia men. Almost 70 individuals have been identified as participants. The atrocity at Mountain Meadows was the work of an entire Mormon community; everyone knew what had happened and everyone knew who had been involved.

"Yet to the eternal shame of the Mormon Church hierarchy, it tried to hush up the macabre events of that day. It attempted to blame the Paiute tribe and then spent many years in various stages of denial."

In an article on the church's website, Richard E Turley Jr., managing director of the Family and Church History Department, writes: "Over the preceding years, disagreements, miscommunication, prejudices and political wrangling on both sides had created a growing divide between the territory and the federal government. In retrospect it is easy to see that both groups overreacted – the government sent an army to put down perceived treason in Utah, and the Saints believed the army was coming to oppress, drive or even destroy them."

Stewart himself became a fugitive. He expressed a desire to return to Scotland "and perhaps do a little good there", but he ended up hiding out in Arizona before fleeing to a Mormon colony in Mexico. Only one man, John D Lee, was tried for his part in the massacre. He was made something of a scapegoat, and in 1877 he was taken to Mountain Meadows, where he was executed by firing squad. As for Stewart, he breathed his last in Mexico in 1895, almost four decades after the merciless killing of the men, women and children of the wagon-train.

Between Daylight and Hell: Scots Who Left a Stain on American History by Iain Lundy is published by Whittles Publishing, priced £18.99. Visit lundyink.com