Carl von Clausewitz (1780 – 1831) has the answer neatly encapsulated for us. Clausewitz was a Prussian general and influential military theorist. He is most famous for his military treatise Vom Kriege (On War). He wrote:- "War is not merely an act of policy but a true political instrument, a continuation of political intercourse carried on with other means."
Just because we, as democrats, reject violence as a 'political instrument' doesn't mean that we should lose sight of its effectiveness nor should we fail to understand that those who practise political violence may in due course become successful, respected and powerful establishment type figures.
Here is how Reuters put it:-
"Former IRA commander and current deputy first minister of Northern Ireland Martin McGuinness will meet the Queen for the first time next week, marking a milestone in the province's peace process.
The queen has never met a senior figure in the now-defunct IRA, which killed her relative Lord Mountbatten in 1979, or its political wing Sinn Fein. The party decided on Friday to sanction the meeting that would have seemed inconceivable a generation ago.
McGuinness, a hero among Irish nationalists who fought a bitter three-decade war against British rule, will meet the 86-year-old monarch on Wednesday during a two-day visit to Northern Ireland as part of her Diamond Jubilee celebrations.
"Today's decision is the right thing to do, at the right time and for the right reasons," said Sinn Fein president Gerry Adams, who, alongside McGuinness, helped end the years of sectarian violence and gave Catholics an equal voice in a power-sharing government with former Protestant foes.
"This is a very significant initiative by us. We don't have to do it, we are doing it despite the fact that it will cause difficulties for some of our own folk but we think it's good for Ireland."
Adams said the party's decision was not unanimous but that a clear majority were in favour of the meeting. He also confirmed that McGuinness would "of course" shake hands with the queen.
Northern Ireland's Unionist first minister Peter Robinson said in a statement the move represented a step forward and was glad that McGuinness had accepted the invite.
"We recognise that this will be a difficult ask for Her Majesty The Queen and a significant step for republicans...(It is) a step forward for Northern Ireland," he said.
The IRA ended its 30-year armed campaign against British rule in 1998, but small splinter groups have continued to launch attacks against British targets, prompting security concerns that have prevented the queen from publicly announcing trips to the province ahead of her arrival.
The June 26-27 visit was the first to be announced in advance since violence broke out in the 1960s and will see the queen and her husband Philip travel to Belfast and Enniskillen, scene of an IRA bombing that killed 11 people at a memorial service in 1987.
The queen, who last visited Northern Ireland in 2010, regularly meets senior Unionist politicians, who want Northern Ireland to stay inside the United Kingdom, but not Sinn Fein, the largest party representing Nationalists who want a united Ireland.
She will meet McGuinness, Robinson and Ireland's president, Michael D. Higgins, at an event organised by the cross-border, peace-building charity Co-operation Ireland.
Adams stressed that the event was "unconnected with the jubilee", allowing McGuinness to meet the queen on terms that were acceptable to his party.
Sinn Fein, which has become increasingly popular south of the Irish border as the main party opposing an EU/IMF bailout, has urged a referendum be held on whether Northern Ireland remain part of Britain where it deputies still refuse to take their parliamentary seats.
It also rejected invitations to attend events during the queen's symbolic visit to the Republic of Ireland last year, the first by a British monarch since Dublin won independence from London in 1921.
The queen has made powerful gestures of reconciliation for Britain's bloody past in Ireland, expressing regret for centuries of conflict, prompting one Sinn Fein mayor to break rank and became the first member of his party to shake the hand of the queen during the trip.
The party has softened its attitude to the royal family since then, agreeing last month not to block Belfast's government from giving the queen a present to mark the Diamond Jubilee, the 60th anniversary of her accession to the throne.
Last year, the party refused to support sending a gift for the wedding of Prince William and Kate Middleton.
"Today's decision reflects a confident, dynamic, forward looking Sinn Fein demonstrating our genuine desire to embrace our Unionist neighbours," Adams said.
"You can rest assured (though) that when Martin McGuinness completes this engagement, he will be as true and as staunch and as active a republican as he is now."
(Reporting by Padraic Halpin. Additional reporting by Lorraine Turner; Editing by Jon Hemming)"