By RONEN BERGMAN Those who leaf through the secret files of any intelligence service know what grave mistakes bad intelligence can lead to. But they also know that sometimes even excellent intelligence doesn't change a thing. The Israeli intelligence community is now learning this lesson the hard way. It has penetrated enemies like Syria, Iran, Lebanon, Hezbollah and Hamas. Yet despite former Prime Minister Ehud Olmert's willingness to authorize highly dangerous operations based on this intelligence, and despite the unquestionable success of the operations themselves, the overall security picture remains as grim as ever. In 2002, then Prime Minister Ariel Sharon appointed his friend and former subordinate, Gen. Meir Dagan, director of the Mossad. Gen. Dagan found the organization lacking in imagination and shying away from operational risks. Mr. Sharon, who knew Gen. Dagan from his days as head of a secret assassinations unit that acted against Fatah in the Gaza Strip during the 1970s, told the general that he wanted "a Mossad with a knife between its teeth." Gen. Dagan transformed the Mossad from top to bottom and made the organization's sole focus Iran's nuclear project and its ties to jihadist organizations. He put tremendous pressure on his subordinates to execute as many operations as possible. Moreover, he built up ties with espionage services in Europe and the Middle East on top of Israel's long-standing relationship with the CIA. In tandem with Gen. Dagan's Mossad revolution, other Israeli military intelligence has also made outstanding breakthroughs. The Shin-Bet (Israel's internal intelligence service), in cooperation with the military, has made huge strides in its understanding of Palestinian guerilla organizations. The results have been tremendous. During the last four years, the uranium enrichment project in Iran was delayed by a series of apparent accidents: the disappearance of an Iranian nuclear scientist, the crash of two planes carrying cargo relating to the project, and two labs that burst into flames. In addition, an Iranian opposition group in exile published highly credible information about the details of the project, which caused Iran much embarrassment and led to International Atomic Energy Agency inspections. On July 12, 2006, thanks to precise intelligence, the Israeli Air Force destroyed almost the entire stock of Hezbollah's long-range rockets stored in underground warehouses. Hezbollah was shocked. In July 2007, another mysterious accident occurred in a missile factory jointly operated by Iran and Syria at a Syrian site called Al-Safir. The production line -- which armed Scud missiles with warheads -- was shut down and many were killed. In September 2007, Israel destroyed a nuclear reactor built by Syria and aided by North Korea in Dir A-Zur -- despite Syria's significant efforts to keep it a secret. With indirect authorization from a very high ranking Israeli official, the CIA published incriminating pictures obtained by Israel of the site before it was bombed. These photos convinced the world that the Syrians were indeed attempting to manufacture a nuclear bomb. In February 2008, Hezbollah's military leader, Imad Mughniyah, was killed in Damascus. In August of that year, Gen. Mohammed Suliman, a liaison to Hamas and Hezbollah who participated in the Syrian nuclear project, was assassinated by a sniper. In December 2008, Israel initiated operation Cast Lead, which dealt Hamas a massive blow. Most of its weapons were destroyed within days by Israeli air strikes. (Israel also knew where the Hamas leadership was hiding, but since it was in a hospital Mr. Olmert refused to authorize the strike.) In January 2009, Israeli Hermes 450 drones attacked three convoys in Sudan that were smuggling weapons from Iran to the Gaza Strip. These are all excellent achievements, but did they change reality? Mostly not. The destruction of the Syrian nuclear reactor seems to have put a temporary end to President Bashar Assad's ambitions of acquiring a nuclear weapon. However, the public humiliation caused by the site's bombing did not sway him from supporting Hamas and Hezbollah and hosting terrorist organizations. Even worse, the heads of Israeli intelligence are now losing sleep over recent information showing that attempts to delay the Iranian nuclear project have failed. Despite some technical difficulties, the Iranians are storming ahead and may possess a nuclear bomb as early as 2010. Hezbollah, although weakened by the 2006 war and Mughniyah's assassination, has become the leading political force in Lebanon. On the southern front, despite the convoy bombings in Sudan, the trafficking of weapons and ammunition into the Gaza Strip continues. Hamas's standing among Palestinians has strengthened. And if a cease-fire is negotiated between Hamas and Israel it would be perceived as a victory for Hamas. The bottom line is that excellent intelligence is very important, but it can only take you so far. In the end, it's the tough diplomatic and military decisions made by Israeli leaders that ensure the security of the state. Mr. Bergman, a correspondent for the Israeli daily Yedioth Ahronoth, is the author of the "The Secret War With Iran" (Free Press, 2008).