Irrespective of how well in advance preparations for an event are made, the unexpected cannot be ruled out.

The July 2005 G8 Summit hosted by Britain in the township of Perth and Kinross in Scotland, we might recall, was overshadowed by the series of co-ordinated suicide bombings of the London public transport system by “homegrown” Muslim terrorists.

At the 2010 G8 Summit with Canada playing the host, the news from Washington surrounding the resignation of Gen. Stanley McChrystal, the commander of U.S. and NATO forces in Afghanistan, could not have come at a more inopportune moment for Prime Minister Stephen Harper.

The general and his staff — according to Michael Hastings’ article, The Runaway General, in Rolling Stone magazine — talked “s—- about many of (U.S. President Barack) Obama’s top people on the diplomatic side.” Hence, Obama was forced to replace the general of his choice with Gen. David Petraeus, head of the U.S. Central Command responsible for the Middle East and adjoining region and the commander who successfully directed the 2007-08 military “surge” in Iraq, as the new military chief in Afghanistan.

The substantive part of Hastings’ reporting on Team McChrystal is the litany of troubles which suggests the war in Afghanistan, fought to save the country from the return of the Taliban, has become bitterly divisive among those responsible for its execution.

The Afghan war appears increasingly unwinnable. This is due to the duplicitous role of Pakistan’s ruling elite through its hirelings in the military’s Inter-Services Intelligence (ISI) providing critical logistical support to the Taliban.

A report published earlier this month by the London School of Economics — The Sun in the Sky: The Relationship Between Pakistan’s ISI and Afghan Insurgents by Matt Waldman of the Carr Center for Human Rights Policy at Harvard’s Kennedy School of Government — documents “a double-game of astonishing magnitude” played by Pakistan with its own regional ambitions as a nuclear weapon state and its hostility towards India.

Waldman’s report is only the most recent analysis of the Afghan situation known to those who have followed the conflict in the area. It also provides the context to explain the restlessness of American military officers in Afghanistan given a task whose endgame — withdrawal of U.S. military beginning in July 2011 — has been announced by Obama to the enemy’s benefit.

Unavoidably, the McChrystal saga will loom over the G8 summit as a bad omen. It raises the question of why any further investment of blood and treasure by America and her allies — particularly Britain and Canada, who have done much of the heavy lifting in the Afghan war — should continue when, in the end, the Afghan ruler in Kabul, whoever he is, will seek an accommodation with the Taliban.

A withdrawal from Afghanistan will not end the terrorist threat to the West and other means to counter it will have to be considered.

But for now, since Afghanistan is on the G8 summit’s agenda, the unexpected developments surrounding McChrystal’s departure require the western leaders come clean with a public grown tired of a war gone longer than any of the wars of the last century.