In October 1968, Martin McGuinness was an 18-year-old assistant in a butcher's shop in his native Derry when local police attacked a civil rights march. McGuinness was not present that day but he was inflamed by his father's reports of the rough handling of the protesters. Within months McGuinness had joined the nascent Irish republican movement.

Read: Northern Ireland Sinn Fein's Martin McGuinness dies, aged 66

Militarily and politically, McGuinness was involved from the beginning to the end of Northern Ireland's Troubles, the 30-year-conflict that left more than 3,000 people dead.

As a senior Irish Republican Army (IRA) commander, McGuinness directly oversaw the most violent armed campaign waged in the UK in modern times. But he also spent a decade in power-sharing government with his once sworn enemy, unionist leader, Ian Paisley.

"There will be some who cannot forget the bitter legacy of the war. And for those who lost loved ones in it that is completely understandable," said former British Prime Minister Tony Blair, who had negotiated the 1998 Good Friday Agreement that finally brought an end to large-scale sectarian violence.

"But for those of us able finally to bring about the Northern Ireland peace agreement, we know we could never have done it without Martin's leadership, courage and quiet insistence that the past should not define the future."

Read: Northern Ireland torn between past and future

Complex character

McGuinness was a complex character. Charismatic and witty, even to strangers, he did not drink or smoke, and was keen supporter of Manchester United, and even the England cricket team. At the same time, he displayed the ruthlessness of a man who led a secret army for more than 25 years and spent time on the run.

McGuinness was an integral part of a generation that brought Sinn Fein - and Irish republicanism - from the political margins to the mainstream. After a decade in the devolved legislature, McGuinness stepped down from his role as deputy first minister earlier this year, triggering an election that saw Sinn Fein returned in record numbers.

But McGuinness' political journey began far away from the marble halls of Stormont, Northern Ireland's imposing seat of government on the outskirts of Belfast. Born into a large Catholic family in Derry, in 1950, James Martin Pacelli McGuinness - the third name in honor of Pope Pius XII - was the son of a foundry worker.

Derry was a city long divided along sectarian lines, with boundaries gerrymandered to ensure a Protestant minority extorted control. As the civil rights movement gave way to armed violence at the end of the 1960s, the young man with the curly hair from the Catholic Bogside area was quickly marked as a future republican leader. McGuinness was part of an IRA delegation that met British secretary of state Willie Whitelaw in 1972 in London.

Politics and armed struggle

By the mid-1970s, power within the IRA had shifted to a younger generation, led by McGuinness and his long-term comrade Gerry Adams. Republicans increasingly pursued a "ballot box and Armalite strategy" combining electoral politics and an armed campaign.

After Sinn Fein's split in 1986, most republicans, and most of the IRA, followed McGuinness and Adams' leadership. The scene was set for a negotiated settlement. But it would take over a decade - and hundreds of deaths - before the peace talks that led to the Good Friday Agreement began.

McGuinness was an obvious choice for Sinn Fein's negotiator in those talks, but the image of McGuinness as peacemaker is not universally shared. Conservative politician Norman Tebbit, whose wife was paralyzed in an IRA bombing, said that the world was a sweeter place now that Martin McGuinness is dead: "He was a coward who posed as a man of peace once beaten," Tebbit said.

Political legacy

McGuinness's more recent political legacy is less controversial. In the immediate years after 1998, he played a key role as both Sinn Fein minister for education and in persuading the IRA rank and file to support peace.

In 2007, McGuinness became deputy first minster - effectively joint leader of the devolved power-sharing administration - alongside onetime unionist firebrand Ian Paisley. Commentators wondered whether a former IRA gunman could work with the notorious Protestant preacher, but the two struck up such a strong rapport that they were dubbed the "Chuckle Brothers."

The election of Arlene Foster in 2016, and the move from multi-party government to a coalition between the Democratic Unionist Party (DUP) and Sinn Fein after May's election, signaled a shift.

Relations between McGuinness and Foster deteriorated, particularly in the wake of last year's Brexit vote. Like the majority in Northern Ireland, McGuinness was firmly opposed to leaving the European Union. 

Read: Sinn Fein leader urges Northern Ireland referendum on UK exit

"He was shocked at the lack of thinking about how we could leave the single market and the Customs Union without a hard border and the risks that posed to the process," recalled Alastair Campbell, Tony Blair's former director of communications at the time of the Good Friday Agreement. "[McGuinness] worried about leaving Europe and he worried about the way British politics was going. He said he was worried Britain was turning into a one-party state."

Northern Ireland's future

Northern Ireland remains politically unstable. Few expect the devolved power-sharing government to be reinstated anytime soon. Meanwhile, the generation of the conflict - of which McGuinness was a figurehead, on both sides of the divide - is being replaced.

Earlier this year, Michelle O'Neill took over as leader of Sinn Fein in Northern Ireland. The 40-year-old over saw the party's best ever election result, finishing just a single seat behind the DUP. For the first time since 1921, unionist parties no longer command a majority leadership in Northern Irish politics.

But McGuinness knew that demographics alone could not deliver his most cherished political dream: a united Ireland. Having spent decades fighting the British state, in later life McGuinness sought to build bridges. A handshake between McGuinness and the Queen in Belfast in 2012 was a defining image of the Northern Irish peace process.

Last November, the Queen unveiled a new royal portrait for her 90th birthday at a ceremony in central London. Martin McGuinness - who was a senior IRA commander when the Queen's cousin Lord Mountbatten was blown up on a 1979 fishing trip - was stood at the back of the room, softy clapping the latest depiction of the British monarch.