The India-Bangladesh border fence project is controversial and behind schedule
By Chris Morris
BBC News, on the India-Bangladesh border
It doesn't look like much. The only outward sign that the long land border between India and Bangladesh has begun is a small white post in the middle of a field, next to the banks of the Ichamati river.
"This is it," says our guide. "Mile Post One."
Just behind us is the first section of a fence that the Indian authorities say will eventually stretch for more than 4,000km (2,485 miles) - the entire length of the border.
"The fence has helped," says Deputy Inspector General Vikash Chandra of the Border Security Force (BSF).
"Wherever we have been able to fence the area, the crime rate has decreased quite a bit."
In the wake of the attacks on Mumbai last November, border security has become a hot political topic.
West Bengal is a long way from Mumbai, but plenty of militants plotting to attack India have crossed this border in the past. It is a vulnerable point.
The border runs through the middle of this village
"Militants are coming," Vikash Chandra admits. "We have learnt that [militant] commanders consider this a safe route. They fly from Karachi to Dhaka and from Dhaka they try to make the crossing.
"We have to make it difficult for them."
It's a huge task. Fence or no fence, the border has never been a barrier to trade - legal or otherwise. And so many people live along its route that mingling with civilians isn't hard.
The border goes right through the middle of the village of Panitar.
In one narrow lane the houses on the left hand side are in India and the houses on the right are in Bangladesh.
Some kids brush a pile of straw away to reveal a weathered stone that marks the actual dividing line.
But the fence - which has to be at least 150 metres from the border itself - has limited Panitar's access to the rest of the country.
"It's a big problem living here," says one of the Indian villagers, Mohammed Abdul Ghani Ghazi. "We waste an hour or two going back and forth through the fence, and we're constantly asked to produce identity papers by the BSF."
It's estimated that there are millions of illegal Bangladeshi migrants in India
Just down the street in Bangladesh, Mohammed Shaukat Ali Ghazi agrees that life has changed.
"We used to go there earlier to visit the bazaars, or for an outing, now we can't," he says.
"Now the fence is there, nobody can go across. Earlier bad people used to come and go all the time, now nobody can. It's not possible."
But other sections of the border are still far less secure, and many of them remain unfenced. The project is controversial, and it's behind schedule.
An hour south of the border by train, on the outskirts of Calcutta, a large community of slum-dwellers lives in small huts by the side of the railway line.
They're cooking on open fires; their laundry is laid out to dry on the stones between the tracks. And most of these people are illegal migrants from Bangladesh.
It's impossible to say how many people have crossed the border in search of work over the years. Some estimates are as high as 20 million.
"Year after year we have people trickling in," says Chandan Nandy, a writer on migration, as we watch a train speed past.
In some places there is no border security at all
"These people might have come 15 or 20 years back. Trying to identify suspected militant from migrant is impossible."
And how much difference does he think the fence has made?
"Not much... but it has increased the cost of migration. Migrants have to pay more to get in.
"The fence is a physical barrier, but money does the talking and the border is a money-spinner. That keeps migration going."
It's not just the Bangladesh border that is a cause for concern, of course.
India's border with Nepal is an open one; and the Line of Control in Kashmir is a place where Indian troops clash regularly with armed militants trying to infiltrate.
"It will take some time before we can say that we have secure borders," admits India's Minister for Home Affairs P Chidambaram. "Given the constraints I think we are working as fast as we can."
Back on the Ichamati river, a night patrol is just beginning close to the point where the land border meets the water.
Out on the river, in the darkness, the idea that anyone can fully secure this border seems rather far-fetched.
But this is one of the front lines, as India scrambles to deter future acts of terrorism on its soil.
"We're better prepared than we were," says Mr Chidambaram. "But I'm not satisfied. We have to work harder."