By Alastair Leithead
BBC News, Herat, western Afghanistan
The pylons get smaller and smaller as they disappear in a long, straight line, across the wide-open, windswept desert, through the heat haze and over the horizon to Iran.
There is more power in Herat than the locals need
In the electricity sub-station just outside of Herat, western Afghanistan, there's the loud hum of power - Iranian power.
More electricity reaches Herat than the city can use, but the industrial park just across the road from the Nato military base is putting it to good use.
Small plastic bottles of fizzy orange juice shuffle along the conveyor belt to be labelled and packed - the building is noticeably Iranian in design and the markings on the machinery show exactly which country helped these Afghan businessmen.
The camels grazing outside cautiously cross the fast, straight, asphalt road - one of the best roads in Afghanistan stretching the 120km to the border.
Soon a railway line will link Afghanistan to Europe, or so boasts the Iranian government.
"We are one of the major donors in Afghanistan," said Mohammad Bahrami, Iranian ambassador to Kabul.
Afghan border guards now watch their Iranian counterparts
"We believe all of the international communities are in the same boat. We have the same destiny in Afghanistan."
Iran has always had close ties with western Afghanistan, and millions of dollars have been spent providing arguably the best infrastructure of any city in the country.
But in the murky world of global politics is the shared destiny he speaks of more about control and influence than charity?
The border policemen cover their faces and cling on to their weapons as the shiny, new, bright-green pickup trucks bump their way along the border patrol route, throwing up choking dust into the back.
The frontier runs for hundreds of kilometres and here, near the border post, both sides eye each other suspiciously from old mud forts and new wooden observation posts.
The Afghans' vehicles were bought by the Americans, and US bases are springing up along the border.
Given the fragile international relations between the US and Iran, there is a much bigger political reason to fight for influence in Afghanistan.
Afghan opium is smuggled between the gaps between observation towers to fuel Iran's four million addicts, and there's increasing concern about what is now travelling in the opposite direction.
"The intelligence reports that we get from our agents in Iran say some weapons come into Afghanistan," said Rahmatullah Safi, the border commander for western Afghanistan.
"The weapons which the enemies use these days such as Kalashnikov, rocket-propelled grenades, heavy machine guns, hand grenades, explosives - they are not coming from the sky, these definitely are coming from across the border.
"Pakistan is kind of doing it openly but Iran is doing it behind the curtain in a secret way, helping the Taleban or the other opposition of the Afghan government."
The Iranian ambassador says his country is a major donor
Every week there is more evidence that the high-powered, hi-tech bombs being used to deadly effect in Iraq are now arriving in Afghanistan.
The commander of Nato's International Security Assistance Force for western Afghanistan (Isaf), Brigadier General Antonio Satta, discovered one cache: "We examined the charges, and unfortunately it is one of the first that is found in Afghanistan. So there are some concerns about it, but hopefully it's an isolated case".
"In Iraq the insurgency developed and they got more and more sophisticated. I believe we are seeing the same thing in Afghanistan, but fortunately they are still quite a long way behind Iraq."
Intelligence sources say Iranian agencies, but not necessarily the government, are talking to the Taleban and that weapons are on the move.
Right now, nowhere in Afghanistan appears to be safe from the insurgency.
Roadside and suicide bombs have been killing soldiers and policemen from the Afghan and international security services, as well as civilians in every corner of the country from Kandahar to Kunduz, Badakhshan to Herat.
The British ambassador for the last year, Stephen Evans, has just left Afghanistan, but he had to deal with at least one case in Helmand.
"I think it was 11 April that a Taleban convoy was intercepted in southern Afghanistan and there was ammunition and explosives of Iranian origin," he said.
Is Iran's investment the latest move in a long-played game?
"Who supplied them, and why, and under what circumstances not yet clear."
Britain already blames Iran for: "backing, financing, arming and supporting terrorism in Iraq," and it suspects the same thing could happen in Afghanistan.
But the Iranian ambassador dismisses the allegations of supplying weapons: "Strongly denied. Strongly denied and we are ready to make that clear," he says.
Beautiful, ancient Herat with its huge citadel towering over the old city and its famous mud brick minarets has a multi-layered history of foreign powers using Afghanistan to expand their empires - to achieve their own global ambitions.
Alexander the Great and Genghis Khan came here. The British fought Persia here in the 1850s when the Great Game with Russia was at its height.
'Long, strategic game'
Rory Stewart, a former diplomat now living in Afghanistan, believes little has changed: "Both here, and in Iraq, the Iranian government's objectives are probably simply to destabilise the situation and deter the US-led coalition from attempting anything against Iran," he said.
"They play very, very long strategic games, and do a lot of very traditional interference in neighbouring countries in order to try to defend their own national interests."
Everyone, of course, is at it - even British, European and American forces are here to protect themselves from terrorism at home - it's another bigger battle being fought in Afghanistan.
And when diplomatic games are played in other lands, it's the people who suffer - it's their lives which are caught up in someone else's war.