This week's groundbreaking visit of Queen Elizabeth II to Ireland is raising passions and security fears in a nation that has traditionally cast a cold eye on its former master.

It is a trip filled with the symbolism of reconciliation as the queen stresses the need to bury a history of often bloody confrontation.

Encouraged by the largely successful peace process in Northern Ireland, which has made her sensitive visit feasible, the queen will become the first British monarch to set foot in the Republic of Ireland. When a British sovereign last came, a full century ago, all of Ireland was still part of the United Kingdom.

"She's doing it for the consolidation of the peace process," said University of Cambridge historian John Morrill, a specialist in Anglo-Irish relations. "It shows the transformation of relations. It is a demonstration to those who still need to be persuaded that things really have changed."

The four-day trip to Dublin, Kildare, Tipperary and Cork comes as a Catholic-Protestant government in the neighboring British territory of Northern Ireland has just been re-elected, marking another peace milestone.

The Irish Republican Army violence of decades past — counting among its victims the queen's cousin, Lord Louis Mountbatten, killed when the IRA blew up his yacht in 1979 — has given way to the group's 2005 renunciation of violence. Only small splinter groups still plot bloodshed across the border.

Irish commentator Fintan O'Toole said the queen should have come to the Republic of Ireland at least a decade ago, when Belfast peacemaking was still in the balance, and her intervention might have boosted the momentum toward peace.

"Her trip isn't actually going to change attitudes. It's putting a seal on changes that have already happened," he said.

"There's been excessive caution about it," he said of the royal visit, first suggested by Ireland's president in 1996. "The authorities are afraid somebody's going to shoot her. But waiting for a time when nobody in Ireland would want to shoot the queen — that's never going to happen."

One of the queen's first actions Tuesday will be to lay a wreath at a Dublin memorial honoring Ireland's rebel dead, a surprisingly direct gesture toward Britain's opponents in the bloody 1919-21 guerrilla war of independence.

While most Dubliners say the queen should be welcomed in an age of exceptionally strong British-Irish relations, some bitterly speak of unhealed national wounds and predict street clashes.

"She should be coming here to apologize for 800 years of oppression. Instead we're all supposed to curtsey and pretend the past never happened. It's sickening," said Eunan O'Kelly, an out-of-work carpenter standing outside Dublin's colonnaded General Post Office, command center for an ill-fated Easter 1916 insurrection that inspired the later war. "People fought and died in this building for our independence. Seems they shouldn't have bothered."

Dubliner Deirdre Walsh, passing by with shopping bags, grabbed a reporter by the shoulder.

"Don't be listening to sourpuss there," she said. "He needs to get a life. This isn't the 1920s anymore. You'd have to be a terrible hypocrite not to welcome the queen here. We're best of friends with the Brits. Half of the Irish have lived in Britain at one point or another. We've got 99 percent of everything in common."

Many Britons believe the queen will be warmly received in Ireland despite the presence of a small group of vocal critics.

Jude Liddle, who owns a wine bar in London, said hostility between the two countries has faded.

"Most Irish people have forgiven us for the bad things we've done," he said. "People who hate Britain won't change their mind based on the queen's visit, or any politician's visit. It's only a small percentage of the population that still care, but the resentment that does exist is strong and won't go away until Northern Ireland is resolved. That's the key to it."

The queen's trip will highlight Ireland's many charms, from the Guinness brewery to its Europe-leading horseracing industry, and stunning historical monuments such as the medieval Rock of Cashel. She will be joined by her husband, Prince Philip.

Security will far exceed measures used for the 1979 visit of Pope John Paul II or for the 1990s visits of U.S. President Bill Clinton.

The national police force has canceled all leave and drafted in officers from rural areas, boosting the security detail to 8,500. They also have borrowed two mobile water cannons from Northern Ireland's police.

The Irish Defence Forces have deployed ground-to-air missiles at key locations, plan to shut down airspace over Dublin and other locations in tandem with the queen's movements, and are keeping more than 1,000 troops in reserve.

Britain's Times of London reported that Ireland's government will allow British police protection officers to carry firearms during the visit.

Several days ahead of the queen's arrival, police began mounting round-the-clock watches and erected security barriers at venues she is scheduled to visit, most crucially Dublin's Garden of Remembrance honoring two centuries of fallen rebels.

A small anti-British pressure group opposed to Northern Ireland's peace process called Eirigi — Gaelic for "rise" — has vowed to take control of the garden two days before the queen arrives. Police say they will be blocked.

Eirigi has plastered Dublin lampposts with placards denouncing the visit — ignoring a Dublin City Council order banning such displays.

The Irish nationalist Sinn Fein party also opposes the visit.

Martin Donnellan, who retired in 2009 as the Republic of Ireland's deputy police commander and is a security consultant today, said anti-terrorist officers in both parts of Ireland were pursuing "a great exchange of intelligence on known terrorists and anarchists and others hellbent on disrupting this visit." He said officers were keeping dissident IRA leaders under close surveillance.


Shawn Pogatchnik can be reached at http://twitter.com/ShawnPogatchnik

Katz reported from London.