AFTER five days of thick fog blocking them, the first American combat troops to arrive in Bosnia landed here yesterday. More than 14 transport planes filled with military vehicles, supplies, and the first paratroopers from the 325th Infantry Airborne Combat Team were expected to land within sight of Serb artillery positions in nearby hills without incident.
Although sniper fire struck Sarajevo for the first time yesterday since the peace agreement was initialed in Dayton, Ohio, Nov. 21, signs are emerging that the NATO peacekeeping mission will face little organized resistance from the Bosnian Serbs.
US military commanders continue to be exceedingly cautious, but the first clear test of how dangerous the American mission will be here will come within days.
While soldiers from the 325th take control of the Tuzla air base from United Nations peacekeepers, a squadron of four US M-1 battle tanks, 13 Bradley armored fighting vehicles, and 130 soldiers from the 1st Armored Division will be establishing a ''secure position'' for US Army engineers to build a pontoon bridge over the Sava River separating Bosnia from Croatia, 40 miles north of here.
''I don't expect anything,'' says Maj. Gary Dornan, an Army spokesman in Tuzla. ''We just want to have the ability to have counterfire if something happens.''
Bridge over the river Sava
The bulk of American forces will enter Bosnia over the bridge and will then have to cross at least five to 10 miles of potentially hostile Bosnian Serb territory before entering the Muslim-held Tuzla area.
US officials say bridge construction will begin within 10 days. They will not say whether the bridge will be built between Croatia and Bosnian Serb-held territory or between Croatia and a small chunk of Bosnia held by friendly Bosnian Croat forces near the town of Zupanja.
The less-risky Zupanja route appears more likely, since it will allow US armor to first cross the bridge and regroup in Bosnian Croat territory before broaching Bosnian Serb territory.
US military spokesmen say the first American patrols into Bosnian Serb territory will likely include several M-1 battle tanks with Apache attack helicopters patrolling overhead to deter any potential threat such as sniping.
While American forces are securing the bridge construction site, British elements of the NATO implementation force, or IFOR, will be sending patrols into Serb territory on Wednesday.
The heavily armed British patrols will act as an initial show of force on the day authority is transferred from Bosnia's beleaguered peacekeeping mission to better-armed IFOR forces.
The peace agreement gives American and British soldiers the right to go where they want on both sides of the front line in Bosnia, roll through rebel Serb or Bosnian government checkpoints, and use force against anyone who tries to stop them.
In a sign that the Bosnian Serbs will not fight implementation of the accord, the Bosnian Serb parliament on Sunday criticized the turnover of Serb-held suburbs around Sarajevo to the Muslim-led government, but called for Serbs to resist by peaceful means.
The self-styled parliament also authorized the negotiated deployment of IFOR troops on Bosnian Serb-held territory.
But in a sign of some lingering hostility, sniper fire hit and wounded a woman riding a Sarajevo tram yesterday. It was the first such fire reported since the new peace accord took effect.
Beleaguered Bosnian Serb ''president'' Radovan Karadzic also announced a cabinet reshuffle that appears to be an attempt to strengthen his steadily diminishing power base. The ouster of the hard-line nationalist is believed to be crucial to the success of the peace plan.
Mr. Karadzic reportedly faces a challenge from more moderate Bosnian Serb politicians allied to President Slobodan Milosevic of Serbia, who negotiated and signed the peace treaty on behalf of the Bosnian Serbs.
But the key to a safe American troop deployment in Bosnia remains Bosnian Serb army commander Gen. Ratko Mladic. General Mladic, who along with Karadzic has been indicted for war crimes, is extremely popular among Bosnian Serbs, exerts tight control over the military, and for now is obeying Mr. Milosevic's wish that the peace accord not be resisted.
Despite the positive signs, American forces are taking no risks. NATO jets could be heard intermittently patrolling overhead as transport planes landed in Tuzla.
The 800 paratroopers in the 325th will be guarding the Tuzla air base and be in range of Serb artillery. They will be armed with a battery of six 105-mm artillery pieces capable of hitting targets eight miles away. Soldiers will be equipped with grenade launchers, 50-caliber machine guns, and 20 Tow long-range antitank missiles.
''I am expecting American forces to be prudent,'' says Army spokesman Dornan.
''But it would not be prudent to fail to provide adequate security,'' he adds.