'War on Terror': Are big military deployments over?

Western forces are racing to leave Afghanistan this month. France has signalled a significant scaling back of its military commitment in Mali. In Iraq, British and other Western forces no longer have any major combat role.

Twenty years after President George W Bush's so-called War on Terror, is the era of big "boots-on-the ground" military deployments to distant warzones coming to an end?

Not yet - there is still a substantial commitment to fighting jihadists in the Sahel - but there is now a radical rethink in how these missions are conducted.

Large-scale, long-term deployments have been hugely costly, in blood, in money and in political capital at home.

The US-led military presence in Afghanistan has cost more than $1tn (£724bn) and thousands of lives on all sides - Afghan forces, Afghan civilians, western forces as well as their insurgent foes.

At their peak in 2010, Western troop numbers topped 100,000. And yet now, after 20 years in the country, the few thousand remaining forces are leaving just as the Taliban looks set to take over more and more territory.

The longer and larger a military commitment is in fighting an insurgency, the more vulnerable it becomes to a variety of potential "Achilles' heels".

The most obvious of these is the casualty rate, a trend that can become seriously unpopular back home.

More than 58,000 Americans died in the Vietnam War and nearly 15,000 Soviet soldiers in Afghanistan - factors that hastened the end of those campaigns. France has lost just over 50 soldiers in Mali since 2013 and its mission there has largely lost its support at home.

Then there is the financial cost, which almost invariably exceeds expectations.

When Saudi Arabia began its intervention in Yemen's civil war in 2015 it never expected to be still fighting there six years later. Estimates of the running cost to the Saudi treasury to date range as high as $100bn (£72.4bn).

Concerns over human rights can also derail a military campaign when least expected.

US air strikes hitting Afghan wedding parties, Saudi air strikes killing civilians in Yemen and human rights abuses by the UAE's allies there have all carried a reputational cost for those countries.

In the case of the UAE, the stories emerging of prisoners being suffocated to death while locked inside shipping containers had a major influence in prompting it to withdraw from the Yemen war.

Then there is the possibility that the host government could end up sharing power with a hostile entity.

In Mali, reports that the government is engaged in secret talks with the jihadists were enough to cause President Emmanuel Macron to threaten to pull out French forces altogether.

In Iraq, says retired British Army Col James Cunliffe, "there is still a real concern about Iranian influence, especially when it comes to the Shi'a militias".

In Afghanistan, the Taliban, who were driven out of power in 2001, are expected to make a comeback. Western security officials say if they end up being a part of the government then all intelligence co-operation would cease.

It is clear that there are no easy answers to the problem of failed states and dangerous dictators. Let's take a look at some recent examples:

So if big, open-ended military deployments are no longer going to be in vogue, then what replaces them?

One clue can be found in the speech delivered on 2 June at the Royal United Services Institute's Land Warfare Conference by the UK Chief of General Staff, General Sir Mark Carleton-Smith.

Today's Army, he said, will be "more networked, more expeditionary and more rapidly deployed, more digitally connected, linking satellite to soldier and centred on a Special Operations Brigade".

Fewer boots on the ground inevitably means a greater reliance on cutting-edge digital technology, including artificial intelligence.

Trends emerging from recent conflicts have prompted a radical rethink in strategic priorities. The brief war in the Caucasus between Azerbaijan and Armenia saw the latter's tanks getting decimated by cheap, unmanned, armed drones supplied by Turkey and directed to their targets at almost no risk to the operators.

Mercenaries, once considered a throwback to a bygone era in Africa, have been making a comeback.

The most obvious example here is Russia's shadowy Wagner Group which has allowed Moscow "plausible deniability" while operating with few restrictions in conflict zones from Libya to West Africa to Mozambique. "A state-centric world order," says Dr Sean McFate, senior fellow at the Washington-based Atlantic Council, "is giving way to a war without states."

None of this means an end to military missions overseas. In Mali and the Sahel the French may be winding up their single-nation Operation Barkhane and sending thousands of troops home. But the UN mission continues and the French are retaining a reduced force committed to a multinational counter-terrorism mission.

In Iraq, the Nato mission will continue to train local counter-insurgency forces and offer them technical support.

In Afghanistan however, the western military presence is disappearing over the horizon at the very time it may be needed most to confront a combined threat from the Taliban, al-Qaeda and Islamic State.