Why Narendra Modi made a U turn on Land Boundary Agreement?

What is the land swap deal between India and Bangladesh?
The land swap deal known as Land Boundary Agreement (LBA) was brokered between former PM Manmohan Singh with his Bangladesh counterpart Sheikh Hasina in 2011. Under the agreement the incongruous Indo- Bangladesh border will be redrawn and made much straighter with each country transferring area under adverse possession and enclaves to the other. Its basic purpose is to end the misery of people who are entrapped in adverse possession areas and thus are bereft of development benefits and make the highly incongruous border straighter for better management.

How much land is at stake?
Under the LBA India will transfer 111 enclaves (land with people belonging to Bangladesh but encircled by Indian Territory) measuring 17, 160.63 acres to Bangladesh and will receive from Bangladesh 51 enclaves measuring 7, 110.2 acres. In addition, India will acquire 2777.038 acres adverse possession areas and transfer 2267.682 acres adverse possession areas to Bangladesh.

Why the UPA government failed to ratify it?
Being a bill meant to redraw country's borders, the LBA is a constitutional amendment bill that requires passage in the parliament. When the UPA government tried to introduce it in the parliament it was met with stiff resistance in the parliament by TMC, AGP and also by the BJP initially. Despite its best efforts the UPA failed to get political parties on board that raised the bogey of UPA government agreeing to lose precious land to Bangladesh.

Why regional parties in Assam and West Bengal are against the LBA?
The regional political parties are raising a bogey against the LBA for populist political reasons. They claim that their states are not only losing vast tracts of territory but also acquiring the baggage of Bangladeshis living in adverse possession areas. The truth, however, is that though India will lose about 10,000 acres of land in all, the LBA will bring long lasting peace on borders.

What was BJP's stand on the LBA earlier?
BJP initially opposed it tooth and nail. In a letter to the secretary of the Rajya Sabha as early as in December 2013, senior BJP leader Arun Jaitely went on to say "My opposition is based on the ground that post-1973 when the basic structure doctrine was introduced by the Supreme Court, the territory of India is an inherent part of the basic structure of the Constitution. Territory of India is a part of the Constitution. It cannot be reduced or altered by an amendment to the Constitution."
However, after background briefings by foreign minister in UPA government Salman Khursheed, the BJP leaders saw the merits of LBA and decided not to oppose it in the winter session in 2013 thus allowing UPA government to introduce it just before parliament session was called sine die.

Why PM Modi has taken a U turn on the LBA bill and showing eagerness to implement it?
PM Modi understands the merits of the LBA. He knows how it can help check illegal immigration by Bangladeshis to a large extent and at the same time help boost the ratings of Sheikh Hasina's Awami League government in Bangladesh. The moderate Awami League government is best bet for India to contain growing Jihadi threat. It has been of a great help in India's fight against insurgent groups and the terrorist organisations like JMB.