ON Friday afternoon, they shoot down an American F-16 jet fighter. On Friday evening, they release 120 United Nations' hostages.
The Bosnian Serbs are again confounding the West by making peace gestures with one hand and then slapping it with the other.
Diplomats and UN officials say the seemingly contradictory signals the Bosnian Serbs are sending may reflect a widening rift between their political leader Radovan Karadzic and their military leader Gen. Ratko Mladic.
"Karadzic and Mladic and their supporters are at odds on how to accomplish the Bosnian Serbs' goals [of establishing a Bosnian Serb state]," says a senior UN official stationed in central Bosnia. "Mladic supposedly favors a diplomatic solution and Karadzic a military solution."
But other officials caution that the Bosnian Serb leadership may be simply trying to confuse their enemies and buy time as they try to decide the fate of the 257 UN hostages they still hold.
"I think you'll see an olive branch. Some will be released, but not all of them," a UN official says. "I think you'll see fighting die down, but it will pick up again, and we'll soon be talking about the guns of August."
Whatever their goal, observers say the Bosnian Serb leadership - already under military, economic, and political pressure - experienced two unexpected political setbacks this weekend.
The West's formal decision Saturday to deploy up to 10,000 additional peacekeepers in Bosnia is a crucial short-term boost for Bosnia's Muslim-led government, which receives the lion's share of UN aid in the former Yugoslavia.
And the unusually forceful intervention of Serbian President Slobodan Milosevic - the Bosnian Serbs' former backer - in obtaining the release of 120 UN peacekeepers on Friday may be worsening reported divisions in the Bosnian Serb leadership.
Some UN officials warn that rising pressure from the Bosnian Army and the new political setbacks could lead Bosnian Serb leaders to finally decide that time is now against them in the conflict. They could try to provoke a full UN pullout and a final military showdown with the strengthening Bosnian Army - while they still hold the military upper hand. "I think that at this point they do" want the UN to leave, says the senior UN official, "because they realize that indirectly we're contributing to the strengthening of the Bosnians."
The fate of the American pilot of the F-16 also remains a potentially explosive issue. How the pilot is treated could signal which direction the Serbs are heading - or simply add to the confusion. Bosnian Serb officials reported they had captured the pilot, but as of yesterday had not produced any evidence to support their claim.
NATO and US officials said yesterday they were still trying to find out if the pilot is alive. The pilot of another F-16 flying alongside saw the missile hit the jet, but did not see the pilot eject. The pilot has a survival radio, but its signal has not been detected.
Why the Serbs shot down the plane remains unclear, according to UN officials. It is possible, but unlikely, that a local military commander made the decision. Surface-to-air missile systems in most Communist-run militaries were tightly controlled by central authorities, and the Bosnian Serb command chain is believed to resemble that of the former Yugoslavia.
With US and European defense ministers meeting Saturday to discuss bolstering the UN force in Bosnia, Friday's downing of the jet came at an extremely sensitive time and could have triggered a major confrontation. "It's certainly a way to discourage NATO," says the senior UN official. "But taken to an extreme, it's a way to invite a major reaction."
The aggressive actions of Mr. Milosevic over the weekend surprised many in the West. He took the unusual step of personally vowing to win the release of all UN hostages from Bosnian Serbs within days - placing his personal prestige on the line.
Milosevic sent Jovica Stanisic, his powerful state security chief, to the Bosnian Serbs' self-declared capital of Pale to accompany the 120 released hostages to Serbia. "We are doing our best to get the others released as soon as possible," Mr. Stanisic told reporters. "We are going to keep on insisting."
But on Saturday Bosnian Serb spokesman Jovan Zametica vowed that all of the remaining 257 UN soldiers would be detained until NATO promised not to use airstrikes.
"We are not going to release the hostages if the option of using force, airstrikes precisely, is not abandoned," he told reporters. Mr. Zametica said the release was a goodwill gesture and discounted Milosevic's role.
Bosnian Serb military leader Mladic is reportedly strengthening his ties with Milosevic during recent trips to the Serbian capital, while Bosnian Serb political leader Karadzic remains Milosevic's apparent political rival.
Karadzic and the Bosnian Serbs' refusal last summer to accept the Western "contact group" peace plan that would divide Bosnia in half between the Muslims and Serbs prompted Milosevic to officially cut off all military aid to the Bosnian Serbs.
Mladic reportedly opposed Karadzic's idea of chaining UN peacekeepers to possible NATO targets. The two also reportedly clashed at a meeting last month, with Karadzic attacking the military for recent Serb military defeats and Mladic responding that government-condoned corruption was draining resources away from the military.
"If the reversal of fortunes continues as it is, I suspect Karadzic's removal could be engineered probably with Milosevic's backing," says the senior UN official. "But ... I think it's extremely important for the international community to realize it is not a war that's going to end tomorrow."