At his home in Iran,
a man is weighing up
whether he should go and fight
in a foreign conflict along
with friends who are already there.
Eventually he decides
to leave his children,
bidding goodbye to Iran's mullahs
too, who will pay him
up to $600 a month as
a mercenary in far-off Syria.
It's a recruitment advert,
aired on Iranian state TV last year,
but there's no mention of money
here, instead an appeal to destroy
Sunni jihadists, including Isis,
and defend the tomb of Zeinab
in Damascus, one of Shia
Islam's holiest shrines.
Iran has recruited an army of Shia
fighters to prop up President Assad,
and to extend an arc of Shia
influence from Tehran all the way
to the Mediterranean,
which has Washington
and its allies rattled.
Iran provides arms, financing
and training, and funnels foreign
fighters into Syria.
It has also sent members of the Iran
Revolutionary Guards to take part
in direct combat operations.
South of Aleppo in Syria,
and the master of those operations
is about to make a very
rare public appearance.
He's Qassem Suleimani,
the commander of Iranian
military missions overseas,
and credited with turning
the tide of Syria's war.
In this adoring crowd are Iraqi,
Lebanese and Afghan fighters,
as well as Iranians,
so he speaks to them in a mixture
of Persian and Arabic,
though they are all fighting under
the banner of Shia Islam.
At first, Suleimani had sent
the Assad regime these military
advisors from Iran's Revolutionary
Guard.
This covert mission ended
in disaster when they were
caught in a cornfield
by a Syrian rebel ambush.
It was too late.
All these men were killed.
This footage was captured by Syrian
rebels, who then published it,
proving that Iran had boots
on the ground,though officials
in Tehran denied it.
Hezbollah was Iran's first
proxy force in Syria,
fellow Shia fighters,
based in Lebanon, but funded
and trained by the Iranians,
diverted by their leader
from their lifelong mission
to confront Israel,
to save President Assad instead.
In 2014, Channel 4 News was given
rare access to the funeral
of a Hezbollah fighter
killed in Syria.
Their losses were mounting
in what had turned into a proxy war
with Sunni rebels funded by Turkey,
the Saudis and other Gulf states.
So Syria's President made
a plea for more help.
The Iranians found that manpower
sympathetic to the cause.
Iraqi, Afghan and even
Pakistani fighters.
Some of them Hezbollah lookalikes.
It was cheaper than using Iranian
men, there was no public backlash,
and it was plausibly deniable too.
Though, by last year,
Iran's Supreme Leader Ayatollah
Khamenei was openly visiting
the families of those who had
died fighting in Syria.
About 1,000 dead,
according to one official.
This religious war is
now too big 
to hide.
And nowhere was Iran more focused
than the battle for Aleppo.
This jeep fighting on that front
is Iranian-armed and Iranian-built.
Russian air strikes paved
the way for victory,
but it's believed up to 8,000
Iranian-backed fighters took
the lead on the ground.
In December their commander,
Qassem Suleimani, made
another rare appearance,
this time inside
the recaptured city.
The architect of plans
to extend Shia military power
across the Middle East,
in a mission which at its most
daring could secure a land corridor
from Iran through Iraq to Syria
and the Mediterranean Sea.
Though the Americans see this
as dangerous Iranian meddling.
Iran is the world's leading state
sponsor of terrorism
and is responsible for intensifying
multiple conflicts and undermining
US interests in countries
such as Syria, Yemen,
Iraq and Lebanon, and continuing
to support attacks against Israel.
Yet for the Iranians,
burying their dead from a distant
war, that war is about challenging
the ambitions of their Sunni rivals
Saudi Arabia and Turkey,
and their allies the Americans.
And any battle in the name
of the Shia faith is, by extension,
a battle for the survival
of Iran itself.
