Spring in Kabul — words that conjure up not flowers in bloom but bombs, destruction and death.

Spring in Afghanistan means the "spring offensive," now so bloodily rooted in tradition that it's announced via email by the Taliban. This year the announcement went out on April 28.

The appalling carnage on Wednesday left scores dead and hundreds injured. A devastating truck bomb blast created a giant crater almost three metres deep in Kabul's Wazir Akbar Khan diplomatic district, home to the presidential palace, to government ministries and to major foreign embassies.

It left the German Embassy looking as though it had been racked by an earthquake. The Canadian Embassy sustained "significant damage" to its first floor, Foreign Affairs Minister Chrystia Freeland said, but embassy staff were accounted for and safe.

Yet despite the fact that this war is being fought by an international coalition of troops, the vast majority of victims, once again, were Afghan civilians.

And this was in Kabul's so-called Green Zone — a term first coined for the area around Saddam Hussein's compound in Baghdad, an area turned into a forbidding redoubt of blast walls and checkpoints created by the invading Americans in 2003 to protect the fearful Iraqi government inside.

Like Baghdad, the centre of Kabul is now a wilderness of blast walls and jumpy soldiers. The Green Zone is a fortress under siege in all but name.

'Cowardly' attack

I was there last year at almost the same period with an international delegation. We were driven at breakneck speed from the airport in a convoy led and tailed by trucks bulging with heavily armed soldiers. We crept into a foreign compound through first one and then a second armoured gate, our cars checked for bombs. We would not be let out except in an armed convoy.

The next morning we awoke to the thump of a bomb. A suicide bomber had boarded a bus a few streets away and had blown himself up, killing 14 and injuring eight. It was one of several deadly bombings around that time.

It was, after all, spring.

In 2016, more than 11,400 Afghan civilians died bloodily — the highest death count since the United Nations started registering civilian casualties in 2009. More than 320,000 Afghans were displaced from their homes by fighting last year.

Afghan officials outside the German embassy in Kabul after Wednesday's blast. (Mohammad Ismail/Reuters)

The Taliban disclaimed responsibility for Wednesday's attack, saying it doesn't target civilians with bombs. ISIS, which has a strong foothold in the east of the country, said nothing in the immediate aftermath.

Ensconced in the presidential palace — a heavily fortified oasis in a land of dust and desert, with its lush gardens and hushed conversation — Afghan President Ashraf Ghani issued a strong condemnation, calling it "cowardly."

In private, Ghani's advisers rail against next-door Pakistan and its security service, which, they say, helps both militant groups in order to keep Afghanistan on its knees as a half-failed state.

Indeed, in announcing this year's spring offensive, the Taliban took ironic pleasure in quoting a report earlier this year by the U.S. inspector general for Afghan reconstruction that concluded the government in Kabul controlled just over half of the 407 districts in the country.

A year earlier the government controlled more than 63 per cent of the districts.

And this after a war prosecuted by the American military for 16 years, a war in which the Americans have spent hundreds of billions of dollars.

U.S. set to prolong war

There are still more than 8,000 American troops stationed in Afghanistan, along with almost 5,000 other NATO troops. This is now the longest war in American history, and U.S. President Donald Trump seems determined to prolong it. There are reports he is about to send up to 5,000 more soldiers to that country.

It would seem a vain gesture. Few American or NATO soldiers now die in this conflict, but their presence ensures that ever larger numbers of civilians are killed.

They are killed because the Afghan military has a soft underbelly. Security contractors speak of the problem of porous defence because it's too easy to bribe someone to look the other way while a truck loaded with explosives is driven in and detonated, even in the Green Zone.

The world is offered appalling images of horror. But the world will soon look away. There will be more bombs and more death.

Other imperial powers before the Americans have entered Afghanistan and left in bloody retreat. It was the case with the Soviet army in 1989. I watched as the Soviet troops marched out with bands playing, trying to disguise defeat with flags and fanfare.

It was the case with the British army in 1842.

In that war, the army of General William Elphinstone was all but annihilated, with up to 15,000 dead. One of the few survivors wrote that it was "a war begun for no wise purpose, carried on with a strange mixture of rashness and timidity, brought to a close after suffering and disaster."

That, one day, may again serve as an epitaph, this time for the American military presence in Afghanistan.