By Robert Windrem
NBC News Investigative Producer for Special Projects

With the arrest Thursday of Ratko Mladic, the two most-hunted fugitives of the Bosnian civil war have been captured, 16 years after being indicted by the U.N. war crimes tribunal on genocide charges.

For years, the U.S. believed Mladic was hiding in Serbia under the protection of hardliners who consider him a hero, and Belgrade's media said Mladic was arrested at the home of relatives in Lazarevo, a village some 60 miles northeast of Belgrade close to the northern Serbian town of Zrenjanin.

But back in the 1990s, after the indictment, the U.S. had an opportunity to “snatch” both Mladic and former Bosnian Serb president Radovan Karadzic but declined.

At the time, U.S. intelligence officials involved in the discussions told NBC News, the U.S. decided not to go after them even after key allied commando and intelligence units trained for such a mission.  In fact, NBC News learned from the officials that U.S. units trained with British commando units throughout 1997 at a British base in Hereford, England, and that U.S. intelligence assets had great success in tracking the two men on an almost daily basis.

The first plans were drawn up in March or April 1997, not long after Karadzic himself had passed through U.S. checkpoints unhindered.

Under the Dayton Accords, the war criminal issue had been left deliberately muddled.  The mandate of the NATO-led peacekeeping force in Bosnia and Herzegovina, SFOR, had allowed it to detain war criminals only if its units encountered them in the course of their duties and if they had enough military backup to do the job.  In other words, a suspected war criminal would practically have to turn himself in at the SFOR camp at Tuzla.

Karadzic's boldness at the checkpoint angered many in NATO.  So planning began for operations that were to target major war criminals particularly Karadzic and Mladic, according to military sources.  The original intention – much debated – was to go after all the higher-profile ones at once ... a big sweep-up operation. (It is unclear if President Bill Clinton originally signed off on this plan or not.  Clearly, authorization for planning and training was given at some level though – not necessarily presidential.)

In addition, NBC NEWS has learned:

• The NATO commander then, Gen. George Joulwan, approved of using SFOR forces to plan and execute these snatches.
• Six or seven major players – countries/organizations – were working on these plans, say U.S. officials.
• The sweep was set to go in June 1997.  Some U.S. Special Operations Forces actually left their bases elsewhere and showed up in Europe ... but Clinton decided against the plan at the last minute. The troops deployed for the operation came home.
• Other nations – particularly Britain – wanted to go after war criminals. So the British told the U.S. they were going to target war criminals they knew to be living in Prijedor, a Bosnian Serb stronghold and the scene of horrific ethnic cleansing. Clinton did eventually sign off on the U.S. intelligence and other support for the British operation.
• Prijedor was a trial balloon, to see what the Serb response would be like.

Deadly shootout, wavering afterward
The raid in Prijedor took place July 10, 1997, and led to a shootout. British troops served the first secret indictments. Simo Drljaca, the brutal former police chief of Prijedor, was shot dead resisting arrest, according to SFOR, “liquidated,” according to the Serbs, who gave him a state funeral.  Another suspect, Milan Kovacevic, was arrested in the same raid and flown to The Hague.

The British wanted to do more. One U.S. official claimed Britain was "shoving the plan in our face" because it felt the U.S. was "dragging its feet in agreeing to execute the whole plan."  Planning began for a September operation. Joulwan was pushing it. 

However, others in the U.S. administration claimed the British plan was too ambitious and the U.S. felt different options provided different advantages.  One Pentagon official says that the U.S. favored more manageable operations as opposed to a large coordinated action, which would be much more difficult to pull off.  Some other U.S. agencies, including the State Department, had lobbied for a big sweep-up.

A military source, however, believed that the political will for this overall mission was intermittent – especially concerning a  large-scale operation.   Many in the Pentagon believed that for an operation to be effective, an element of surprise was important, and after Prijedor, the Serbs became nervous, fearing more missions. "You'd pretty much have to wait 60-90 days anyway to regain any such element of surprise,” the source said.

While nothing was approved, U.S. Special Operations Forces nevertheless began training for such "Big Fish" missions. U.S. Navy Seals and the Army Delta Force trained for months in Hereford with the British SAS on very specific targets.  There was also planning and training in Germany, apparently in Grafenwoehr and Stuttgart.

Tracking the men
The decision not to go ahead with the mission was not based on a lack of intelligence. 

Karadzic and Mladic were tracked intensely from the time of the Dayton Accords in 1995 onward, but inside the CIA's Balkan Task Force, there was always uncertainty about whether the U.S. wanted to grab either of them, fearing the implications.

"The CIA always wanted to know where they were, but pinpointing was the problem," said one official. 

The U.S. usually knew the general area where they were hiding on a daily basis, but tracking them to a particular village or home wasn’t easy.  On some days, intelligence was better than others, but the U.S. usually knew within a 20-mile radius where they were, said one official.

Karadzic and Mladic usually moved three times a week, sometimes every day, mostly at night. And they moved independently.

Often, they could be found operating near Tuzla ... even when U.S. troops were operating there.   One official described the lack of a will to grab them as "very frustrating."   They were also known to operate near Mostar, which is on the Bosnian-Croatian border.  They often surprised the U.S. with their arrogance.

The primary means of intelligence was electronic eavesdropping, known as "sigint" or "signals intelligence" in the spy trade.

"Humint [human intelligence] is obviously the best, but it was very hard. We never had good humint.  They operate in small villages and villagers were tight-lipped. They are both too afraid and too loyal to tell us anything valuable," said one source.

Still the U.S. did have some human sources, and U.S. officials believed Karadzic was probably more vulnerable to a U.S. penetration of his bodyguards since they were non-military men and paid in hard currency. 

Arsenal of eavesdropping
The U.S. also knew from intelligence gathering that there were increasing strains between the two men and their cadre.

Mladic and Karadzic and their people used cell and landline phones to communicate, and U.S. intelligence took advantage of that.  "We had the cell phones covered, we had the land lines covered. They used either, we got it."

The primary means of intelligence collection was the RC-135 "Rivet Joint" aircraft.  A converted Boeing 707 loaded with antennas to pick up conversations, it flew regular missions out of Mildenhall AB, near London loitered over Bosnia at 35,000 feet for up to 10 hours as it recorded conversations and then flew back to England. There was at least one Serbo-Croatian linguist on board the aircraft to sift through communications, separating important calls from the routine traffic.  Further analysis is done on the ground as well as back in the U.S..

The U.S. also used U-2 spy planes and satellites to eavesdrop and photograph suspected locations.  In addition, the CIA flew Predator drones out of Albania, and covert ground stations were set up in Bosnia and Croatia to help track their communications. 

All the intercepts were fed into National Security Agency headquarters at Fort Meade, Md., for enhancement and to the CIA for analysis.

Mladic and Karadzic knew they were being tracked.  At one point in 1996, Mladic ordered his men to write the words, "F*** YOU" in English, in the snow near the town of Brcko, so it could be seen by spy satellites.  The image was shown to Clinton in the White House and he got a good laugh out of it, said one official who was in the room.

Long-sought war crimes fugitive caught in Serbia

The bottom line, some officials believed, was that the U.S. was not interested in grabbing Mladic or Karadzic.  The U.S. knew doing so would complicate the Dayton Accords and the Balkan situation in general and could hurt relations with Russia, which protected the Serbs.

"I never heard from the principals that we have to find them," said one official involved in tracking them. "There was no priority getting the top guys.  The priority was to grab the lower-level guys to satisfy public concerns about war crimes."

The CIA, however, kept track "in case the policy changed, and in the Clinton administration, foreign policy, especially Bosnia, was subject to the polls. We feared that one day, someone – like the president – would demand to know where these guys were."

Several members of the Balkan Task Force remembered when Air Force Capt. Scott O'Grady was shot down and a delegation was called to the White House Situation Room to brief the president on where O'Grady might be.  "The president blew up, demanding to know why O'Grady couldn't be found when the U.S. was spending $30 billion on intelligence."

The CIA was very frustrated by the White House's lack of interest in grabbing war criminals, knowing the level of war crimes alleged to have been committed. "I read the interviews with rape victims and it was one of the worst things imaginable," said one CIA official.