The general masterminding the most awesome bombing campaign in Europe since the second World War, from his headquarters in Mons, Belgium, knows his enemy all too well.
Four-star Gen Wesley Clark spent weeks with President Slobodan Milosevic and Serb senior officers as the peace agreement for Bosnia was being hammered out at Dayton, Ohio, in 1995. When the NATO air strikes began last week, Clark telephoned the Yugoslav chief-of-staff and warned him to keep his small navy in port or risk its annihilation.
At Dayton, Clark was the architect of the military chapter of the agreement which allowed NATO to act as a peacekeeping force in Bosnia. He is credited with persuading Milosevic to agree to a corridor to give a Muslim area access to Sarajevo. It was nicknamed "Clark Corridor" or sometimes the "Scotch Road", a reference to the heavy night-time drinking at Dayton recorded by Richard Holbrooke in his book.
It is hard to associate heavy drinking with the small, intense general who appears at the NATO briefings in Brussels promising "to systematically attack, disrupt, degrade, devastate and, ultimately . . . destroy" the forces of Milosevic. The NATO Secretary-General, Javier Solana, felt obliged to withdraw the word "destroy" as the general had gone further than his political masters were prepared to allow.
But Clark is no blood-and-guts general, threatening to bomb the Serbs back to the Stone Age. This is a Rhodes scholar who holds a master's degree in philosophy, politics and economics from Oxford.
He was in Oxford at the same time as another Rhodes scholar who did not bother to finish his degree, one William Jefferson Clinton, who is now Clark's commander-in-chief. Clinton was then dodging the call-up for Vietnam and reportedly joined anti-war demonstrations.
Clark instead argued for American participation in debates around other universities, usually outnumbered by his opponents. Curiously, he and Clinton are from Arkansas and are almost the same age. Both were brought up as Southern Baptists but Clark has since converted to Catholicism. And both are married with one child.
As Clinton went back to Arkansas, after a law degree at Yale, Clark, who had graduated with a first place at West Point in 1966, headed for Vietnam. As a lieutenant, he was wounded four times and won the Silver Star and Purple Heart.
He displayed bravery again in Bosnia during peace negotiations with the Serbs. When an armoured vehicle carrying three of the US diplomats plunged off a mountain road, Clark, who was following, insisted on climbing down the heavily-mined mountain to try to rescue the victims from their burning vehicle.
They died, however, and Clark and Holbrooke are said to hold their deaths against Milosevic, who had refused the group permission to travel by air.
After Vietnam, Clark was brought into the Nixon White House as a military adviser and got a valuable grounding in politics and diplomacy.
He went back to the army and rose steadily, winning a high reputation for training and organising large-scale operations. In 1994 he served as military adviser in negotiations with the Serbs.
Clark committed a gaffe when he was photographed swapping caps with the Serb commander, Ratko Mladic, who was held responsible for atrocities against Muslims and is now a designated war criminal. But Clark's skills in the Dayton negotiations boosted his reputation.
He was promoted to command the southern US forces in Panama and two years ago was appointed Supreme Allied Commander in Europe (Saceur) as well as commander of all US forces stretching to the Middle East.
Now Clark is facing the biggest test of a brilliant career. Success could mean eventual promotion to the pinnacle of chairman of the joint chiefs-of-staff.
A former classmate, John Wheeler, has described Clark to the Washington Post as "a dashing general, a guy who can be a charmer. But he's a killer. He knows where the jugular is."
According to some former colleagues he is not all that well liked in the US army. "He's not particularly popular among the folks," is how a retired major general described Clark to the Wall Street Journal.
Perhaps the intellectual brilliance has something to do with it. One magazine profile said Clark "laces his talk with words like `dendritic' and references to The Forgotten Soldier, a German first World War memoir."
He has not been afraid to state his views on the limitations of the present air campaign. His assertion that "there is no way air power can stop the paramilitary from carrying out their campaign of ethnic cleansing" was not exactly the message being heard from Washington, where the air strikes were first hailed as the way to stop the humanitarian catastrophe.
Even last year, Clark was warning in a lecture that Kosovo would be "the ultimate Balkans firestorm". Now he is in the middle of it.