President Donald Trump has upped the ante in America’s longest-running war, but it is not clear whether an all-guns-blazing strategy will bring the long-running conflict any nearer to a conclusion.

In a clear departure from approaches applied by his predecessors, George W. Bush and Barack Obama, Trump proclaimed a new mission in Afghanistan in which he served notice on Pakistan that it would be required to participate more vigorously in the war against the Taliban.

This was a pointed reference to long-standing US disquiet about Pakistan turning a blind eye to Taliban leaders who have taken refuge in its remote regions.

In his nationally televised address – the first of his presidency – Trump provided no details of an additional troop deployment, nor did he describe how a change of strategy might play out. However, he indicated much more authority in the conduct of the war would be vested in generals on the ground to enable them to take the fight to the enemy.

Trump’s warning to Pakistan to co-operate in efforts to stabilise Afghanistan or bear the consequences represented a striking departure from a less-confrontational approach of past presidents.

His speech sets the scene for a more aggressive American war-fighting strategy in Afghanistan and South Asia more generally.

Apart from announcing the US would take the fight to the Taliban with Pakistan expected to pull its weight, perhaps the most important component of the Trump speech was his declaration that his country’s nation-building days are over. He said:

We are a partner and a friend, but we will not dictate to the Afghan people how to live or how to govern their own complex society. We are not nation-building again. We are killing terrorists.

This suggests a departure from the approach adopted by the US and its allies since 2001, in which enormous effort has been committed to helping Afghanistan establish a civil society.

Whether Trump was declaring an end to – or lessening of – these efforts remains to be seen. But it would seem to be counterproductive to abandon welfare and educational programs aimed at combating Taliban influence on the ground.

A more aggressive American war-fighting effort will inevitably pose challenges for participants in NATO-led operations in Afghanistan, including Australia.

Australia recently increased its Afghanistan commitment – Australian service personnel in Afghanistan number 270 – to train and mentor Afghan forces, but officials have made it clear this will not involve frontline roles.

Trump’s new strategy might require Australia to review this decision. It should hasten slowly.

Trump acknowledged that since becoming president he had undergone a change of heart on Afghanistan, having previously urged withdrawal on the basis that the US was involved in an unwinnable war.

In deliberations that brought a shift in his position, Trump cited three main factors. These were:

• The US needed to honour the sacrifice of its soldiers who had fallen in Afghanistan.

• Withdrawal would risk creating a fresh vacuum for terrorists.

• The US faced a broader terrorist threat in Afghanistan and South Asia that required its continued presence.

These conclusions are not much different from those reached by Bush and Obama as the rationale for keeping American troops engaged. What is different is the policy’s hyer-aggressive tone. Trump declared:

Our troops will fight to win. From now on victory will have a clear definition. Attacking our enemies, obliterating ISIS, crush al-Qaeda, preventing the Taliban from taking over Afghanistan, and stopping mass terror attacks against America before they emerge.

All this will be easier said than done. In the 19th century, Britain was unable to pacify Afghanistan, in the 20th century Soviet efforts were rebuffed, and now in the 21st century America and its NATO allies have struggled.

The reality is that despite 16 years of NATO involvement, spending one trillion dollars and the deaths of more than 2,200 Americans, 10% of Afghanistan remains under Taliban control – and another one-third is contested.

In 2016, 11,418 civilians died in the continuing war, and 660,000 fled their homes. Conflict was up sharply last year from the year before. The Afghan regular army continues to be bedevilled by poor morale and desertions.

All this suggests the Taliban, and other terrorist groups, including Islamic State and al-Qaeda, are deepening their engagement in the country.

None of this augurs well for a renewed push for victory by US-led NATO forces whose main mission has been to hold the country together in the hope an effective leadership emerges. This has been slow to eventuate.

Trump and his generals, including three of his closest advisers – chief-of-staff John Kelly, Defence Secretary James Mattis, and national security adviser H.R. McMaster – would be well aware of the challenges. But in US efforts to either beat the Taliban into submission, or force it to the negotiating table, they have clearly persuaded Trump there is no choice but to intensify America’s combat operations.

We should expect significantly increased loss of life and inevitable collateral damage, including non-combatant casualties. This will be the reality.

The question will then become whether the new Trump doctrine of using overwhelming force against Islamic terrorists buried in their local communities will have proved the best investment of American resources.

All this remains problematic. What’s not in question is that the US has a commander-in-chief who can be expected to exhibit less squeamishness than his predecessors about the risks involved in waging a war whose success will be difficult to measure.

What should not be forgotten is that despite the deployment of 140,000 American troops in 2011 as part of a surge aimed at enabling a beleaguered Afghan regime to stand on its feet, the Taliban quickly reasserted itself once US forces were drawn down.

Trump and his advisers would not need reminding that Americans are sick of these wars, and their cost in lives and money. Trump campaigned against further such commitments. Now he’s changed his mind.