The person primarily responsible for Sri Lanka‘s victory over the LTTE in May 2009 is Mahinda Rajapaksa, the current President of Sri Lanka and Comman

http://www.island.lk/2010/06/13/features6.html
Winning the Eelam War
by Kamalika Pieris
The first three Presidents of Sri Lanka made no effort to win the war, though victory was possible. J.R. Jayewardene was forced by India to halt the Vadamarachchi operation (1987) which would have permanently ended the LTTE offensive. Premadasa handed over arms, ammunition, cement and cash to the LTTE. The LTTE used the ammunition and arms to kill 600 policemen in 1990. In Kumaratunga’s time, the army was almost wiped out at Mullaitivu (1996). A weeping soldier said the men had nothing to resist the LTTE with except a pistol and few grenades. Four years later, soldiers died of dehydration at Elephant Pass.
These Presidents helped to strengthen the LTTE and weaken the army. LTTE was able to bring in large shipments of arms, ammunition and equipment since coastal defence was neglected. Unsatisfactory military equipment caused chaos in the battlefield. Sia Marchetti and Pucara planes bought in 1993 were soon grounded. By 2005, around 26,000 soldiers had died.
The person primarily responsible for Sri Lanka‘s victory over the LTTE in May 2009 is Mahinda Rajapaksa, the current President of Sri Lanka and Commander in Chief of the armed forces. Rajapaksa did not get on an elephant and go to war, but he was the force behind the war. He withstood enormous international pressure and pursued the war with determination. He monitored its progress and took necessary decisions.
He managed international relations skillfully. He strengthened diplomatic ties and persuaded several countries to sell arms to Sri Lanka. Israel replaced two UAVs shot down by LTTE without any charge. When India refused to sell arms, Sri Lanka turned to China. A bilateral body was set up to maintain continuous dialogue with India and keep it supportive. India was kept briefed at all times Sri Lanka could have won the war three weeks before May 19th. But this would have affected the election prospects of India’s Congress Party in Tamilnadu. Rajapaksa therefore held back the troops. Once Tamilnadu went to polls, he ordered the army to finish the job before the next government was installed in New Delhi.
The next person responsible for the victory was Defence Secretary, Gotabhaya Rajapaksa, brother to the President. Lalith Weeratunga said that he had never seen such a tech-savvy, resolute, no-nonsense Defence Secretary as Gotabhaya. Gotabhaya had been a career officer in the Sri Lanka army. He had received training in India, Pakistan and USA and had won two awards for bravery in action. He had been a commander at Vadamarachhi and Operation Thrividabalaya.
Gotabhaya was the mastermind behind the war. As early as 2006 he had submitted a long list of expensive war equipment he wanted purchased because he wished to be well prepared. He said "I knew that if we had a committed team, right planning, required numbers and the weaponry we could achieve our goal. I was not ready to give in to anything or anybody." He sued a newspaper that made defamatory allegations regarding the purchase of MiG 27s and refused a settlement out of court.
He had unreserved access to the President and was the link between the President and the armed forces. He was a good tactician and personally handled intelligence. Weeratunge observed that Gotabhaya cared about the lower ranks of the armed forces. He said most Defense Secretaries did not know the plight of the soldiers and did not bother about things like houses for them but Gotabhaya did. He knew their problems and looked into them.
Gotabhaya selected the Service commanders including Fonseka and ensured that the three armed forces worked closely together. He was in close contact with the ground commanders at all stages of the battle. He sorted out their logistical problems and at times directly intervened to facilitate coordination between the different forces. Details were looked into and requests processed quickly. His leadership style included supporting as well as directing.
For the first time, the government followed a carefully planned strategy against the LTTE.War operations, from 1976 to 2002 were studied to find what had gone wrong. .They found nothing wrong with the armed forces and concluded that they could win. The armed forces were increased to 450,000 with 300,00 for the army. A dozen new fighting formations were created "LTTE thought that we didn’t have sufficient troops to hold the east and we lulled everyone into believing this," said Gotabhaya. "When Mavil Aru was blocked, we were ready"
The government somehow managed to purchase the necessary military supplies despite cash flow problems and the need to keep the economy afloat. It set up a company, Lanka Logistics and Technologies for arms purchases. The directors were Secretary to Treasury, Secretary for Defense, Chief of Defense Staff, the three Service Commanders and the IGP. Local agents of foreign arms dealers were excluded. The company dealt directly with foreign governments. Purchasing procedures were trimmed and purchase approvals speeded up. This had needed some heavy handed measures by Gotabhaya. Arms purchases were based on recommendations of the military with Gotabhaya making the final decision. Fighter aircraft were purchased. Also, different bombs for different targets.. Earlier there was only one type of bomb for all targets. Sri Lanka could have saved a lot of money if it had set up this organization decades earlier.
Defying accepted military strategy the army attacked the enemy at their strongest points, not the weakest. This took LTTE by surprise. . The army fought on several fronts simultaneously. Nearly all assaults were made in heavily mined areas. The momentum was never allowed to slacken. Instead of the large formations used in the past, the army was trained to fight in small teams of four and eight. These teams were trained to go forward on their own. They succeeded in advancing eight to 12 kilometers per day.
Initially they did not go for territory but went for the LTTE itself, killing and injuring as many as possible. LTTE were harried in all directions and eventually lost their most experienced fighters and also their morale. The army then started taking territory. In ten months, it reached Pooneryn in the north west and neared Mullaitivu on the east.
Modern wars are not won solely on the ground. Navy and air support are essential. LTTE had eight merchant ships that were bringing in ammunition. They were floating warehouses carrying an arsenal which would have sustained the war for years. These ships were destroyed in 2006 and 2007. This task, which took years to plan, was executed to perfection by the aging Sri Lanka fleet. LTTE could not land a single shipment of arms thereafter and started retreating on all fronts.
The air force took on several LTTE targets from the air. They destroyed strategic locations and artillery positions. They went at bunkers, camps, munitions dumps and fuel dumps. Some dumps had two or three hundred thousand liters of fuel. They attacked Sea Tiger bases, hit concealed vessels and boat building yards. They forced the LTTE to shift their daytime training to night. LTTE leaders also had to go underground. Planes provided air support for the ground attacks, clearing the way for advancing troops. At Puthukudirippu the helicopter squadron flew many sorties, day and night. "It was like 31st night".
The Air Force never gave in. When LTTE attacked Anuradhapura air base in Oct 2007, they went after Tamil Selvam and killed him. This stunned the LTTE and damaged its morale. The LTTE acquired air capability, with light fixed wing aircraft. This was the first ever air threat to a conventional air force by a terrorist organization. Air force countered it with an air defense network, put together within the record time of one year. It usually took five to eight years to set up such a network.
After every LTTE attack in Colombo the facilitators and supporters who provided intelligence, finance and housing for the attack team were arrested. The government set up checkpoints and roadblocks, raided lodges, conducted cordon and search operations. These measures were unpopular at the start, but they helped break the rich LTTE support network in Colombo and elsewhere. Collaboration between the military, police, and intelligence service led to the strangling of the LTTE in the south, reducing their ability to operate effectively specially in Colombo.
Sri Lanka took two years and ten months to eliminate the LTTE from its illegal occupation of territory in the north and east. LTTE positions were taken in 2007 and 2008, first in the east and then in the Vanni. Paranthan, Oddusuddan, Elephant Pass, the administrative centre, Kilinochchi and the naval headquarters, Mullaitivu fell in succession in 2009. The LTTE leaders were not allowed to get away. They were cornered and killed. There was a naval blockade at Mullaitivu and planes at China Bay to prevent them escaping. On May 18 Army Commander Fonseka had told President that the end could not be achieved within the day. This was contradicted by the field commanders and victory was declared on May 19 2009.