At the height of the Cold War, two US airmen monitor their radar screens at a quiet and remote NORAD facility in Alaska. Suddenly, one of the bored operators notices an unexpected blip on his radar screen. It appears to be an unidentified aircraft sneaking in on the leading edge of a weather front. He alerts his partner about the threat and begins to contact Elmendorf AFB. The other airman retrieves a silenced pistol from his desk and kills him. He then proceeds to shoot the remaining station personnel while they are sleepng in their bunks. Lighting a cigarette, the traitor notifies Elmendorf that the station will be out of commission for the next hour in order to repair a malfunctioning generator. The necessary blind spot has been created.
Out of the oncoming snowstorm, dozens of camouflaged parachutists glide to earth from a transport plane. On the ground, they unpack their equipment, clearly marked "CCCP," and form up behind a small, tracked command vehicle before setting out on cross-country skis. At a nearby bush cabin, an elderly couple is usng their shortwave radio to communicate with Fairbanks and report on the intense storm. Hearing the dogs barking outside, the old man goes to investigate. His wife immediately hears automatic weapons fire and tries to use the radio to call for help before she is also gunned down by Soviet troops in ski parkas.
The scene shifts to Washington, D.C., where widowed President Thomas McKenna (Rock Hudson) awakens from a bad dream and groggily climbs out of bed. He dresses and goes downstairs to the Oval Office, where he gets a daily briefing from political advisor Richard Hickman (James Hampton). The US has been leading an international grain embargo against the Soviet Union, leadng to civil unrest in Russian cities, decreased grain exports for American farmers, and declining popularity for McKenna.
Back in Alaska, a US National Guard unit is out on maneuvers. Unaware of the Soviet incursion, they noisily approach the recently attacked bush cabin out of a blinding snowstorm. As they gather in front of the cabin, they are quietly surrounded by the lurking Soviet pathfinder unit. On a signal from the Russian commander, Colonel Vorashin (Jeroen Krabbe), the Soviet troops massacre the unsuspecting Guardsmen. Only one wounded American soldier escapes with his life, falling over a steep snowbank and going unnoticed.
In Moscow, a worried Secretary Gorny (Brian Keith) is dealng with food riots and general strikes. It is revealed that Russian hardliners led by General Rudinski (Robert Prosky) of the KGB have secretly put the risky Alaska incursion in motion without consulting Gorny. The hardline conspirators hope to pressure the US into abandoning their punitive grain embargo.
Simultaneously, Colonel Jake Caffey (David Soul) assumes his duties as Deputy Brigade Commander at Ft. Wainwright in Alaska. His by-the-book commanding officer makes it clear that Caffey wasn't his first choice for the post. At a Christmas party in his honor, Caffey encounters the newly-assigned Intelligence Officer, Major Kate Breckenridge (Cathy Lee Crosby), with whom he had previously conducted an affair. The aggressive and attractive Major Breckenridge makes it clear that she would like to pick things up where she left off with newly separated Colonel Caffey.
The ambushed National Guard patrol is soon reported missing. Caffey is sent out into the field to investigate. After meeting up with the remaining National Guard troops, Caffey and a few men mount snowmobiles and soon come across the dying Guardsman. He manages to tell them enough to alarm Caffey. He and his men quickly reconnoiter the area, spot the Soviet ski column and incredulously report the incursion to Ft. Wainwright. The supercilious commanding general ridicules Caffey's story but decides to take a look for himself. Accompanied by Major Breckenridge, the commanding officer takes a helicopter flight directly to Caffey's location, giving their position away and infuriating Caffey. While the General observes and vacillates over a plan of action, Soviet marksmen sneak up and open fire, killing the General. An intense firefight erupts, with several casualties on both sides. The outnumbered Americans retreat to their helicopter and escape.
Back in Washington, an emergency meeting is convened in the White House situation room. Predictably, the meeting breaks down into hawks and doves. Military options are severely limited by the heavy weather. President McKenna tries to buy time, insisting on absolute secrecy and restraint while he figures out what the Soviets are up to. He places a call to Colonel Caffey and implores him to nip at the Russians' ankles and slow them down. Despite the fact that Caffey has few assets to work with, he agrees to do what he can. Looking for a chokepoint, Caffey and his men plot the most likely Russian line of advance and then mount up on helicopters to intercept them. They overfly a small industrial installation near the Brooks Range and soon discover that it is a launching valve station along the new Alaska Oil Pipeline. It backs up to a mountain pass and offers the needed chokepoint.
Lightly armed and short on preparation time and ammunition, Caffey quickly improvises a "buzzsaw" defensive strategy, utilizing numerous lengths of pipe scattered in front of the station at assorted angles. His handful of soldiers will shelter inside the sections of pipe, facing the enemy and creating interlocking fields of fire. The station is only vulnerable to a frontal assault. As the Americans nervously await, the Soviet troops soon appear out of the snowstorm and cautiously advance, unaware of Caffey's well-hidden force. The Americans open fire and achieve complete surprise, taking a heavy toll on the Russian forces, who only respond with small arms fire. Knowing that the Russians are surely carrying heavier weapons and yet refusing to deploy them, Caffey Is puzzled by their tactics. He interrogates the station operator about the purpose of the facility. The operator explains that the valve station is used to insert cleaning scrapers into the pipeline, sending them downstream for many miles. It suddenly dawns on Caffey why the Russians need to capture the facility intact. Floating mines with delayed fuses could easily be inserted into the pipeline from the launching station and sent downstream, destroying many miles of pipeline and severely restricting American energy supplies for the foreseeable future.
Both sides are under pressure due to the harsh weather, but for different reasons. American airpower is virtually useless in such low visibility conditions, and all air assets remain grounded. The Russians need the bad weather to hold until they have completed their mission. The continuing stiff resistance from Caffey's men has thrown the Russian operation seriously behind schedule.
Secretary Gorny, angry with his own subordinates over their dangerous "adventure," requests a secret meeting with President McKenna on neutral ground in Reykjavik, Iceland. Before he leaves, McKenna's military advisors urge him to go to a Defcon 3 defensive posture as a precaution against further Soviet aggression. Fearing the dangerous escalation that could result, McKenna declines for the time being. The summit meeting between McKenna and Gorny is tense. McKenna condemns the Russians for their unlawful, unprovoked invasion of US sovereign territory. Gorny responds that the US created the standoff through an immoral embargo that deprives the Russian people of food. Charges and countercharges are traded with no resolution. Gorny warns that his troops can put the pipeline out of commission for several years. McKenna demands that the Russians withdraw and explains that the American people and their government will never submit to blackmail.
At the Alaskan valve station, the standoff continues. Both sides tend to their wounded and wait. The Americans are down to their last few rounds. Caffey's second-in-command takes it upon himself to break the stalemate. He carefully infiltrates Russian lines and hurls a grenade into the Russian command vehicle before he is killed. Several Russians, including Vorashin, are badly wounded.
Aboard Air Force One, a visibly shaken President McKenna reluctantly orders Defcon 3. He contacts Caffey and implores him to hold out. The tiny force holding the valve station represents the difference between a skirmish and World War III. When the Russians realize that the US has ordered Defcon 3, they counter with their own Red Flag configuration. To drive home their point, a Soviet warship rams a US naval destroyer in the Arabian Sea. Under extreme pressure, President McKenna orders Defcon 2. Things are spiraling dangerously out of control.
In Alaska, Colonel Vorashin is contacted by Gorny and reminded how critical his mission is. Gorny lets slip that they are trying to avoid a nuclear war. Colonel Vorashin is alarmed by the comment, but General Rudinski seizes the phone and reassures Vorashin. He orders him to mount an all-out assault on the valve station. Rudinski also ups the ante by sending several squadrons of nuclear-armed Backfire bombers towards the US Pacific coast. Gorny pleads with Rudinski to withdraw the Pathfinder unit, recall the nuclear bombers, and defuse the crisis, but Rudinski brushes it off. Gorny is no longer in control.
Vorashin's men make their final push on the station. The Americans in the "buzzsaw" inflict as many casualties as possible before abandoning the perimeter and withdrawing inside the station. The Russians use a satchel charge to blow the main door and force an entry. Once again, the Americans exact a heavy toll, but the overwhelming Russian firepower forces them to retreat deeper into the facility. Kate Breckenridge and the civilian station operator are both killed in the firefight. Although he is about to gain control of his objective, Vorashin now requests a parley with Caffey. As the two opposing warriors stand face-to-face, the weary and disillusioned Vorashin proposes a truce. He tells Caffey that Moscow has much bigger objectives than he had realized. He offers to withdraw and deprive the warmongers of their victory. A hopeful Caffey accepts Vorashin's overture, but it is not to be. Just as the two men clasp hands, the Soviet unit's political officer tosses a grenade between them. The station falls to the Russians.
In Moscow, Secretary Gorny's limousine explodes in a fireball. Rudinski is now firmly in control. When President McKenna is advised that Russian Backfire bombers are en route, he orders American B-1s into the air. McKenna is stunned when a planned emergency conference call with Gorny instead involves the hardliner Rudinski. Rudinski claims that Gorny has been taken ill, but McKenna knows they have killed him. Rudinski renews his demand for an end to the embargo. McKenna again refuses to be blackmailed and informs Rudinski that American B-1s are in flight. Alarmed, Rudinski concludes that the US is actually going to attack. He lies to McKenna and offers to immediately stand down and withdraw all Russian forces, but he is only buying time for a nuclear first strike, believing that McKenna will need Congressional approval to initiate an attack. Rudinski gives the fateful "go" order. On the other end of the phone, McKenna realizes that the Russians are coming in and declines to wait on an approval that would delay the American nuclear response. He tearfully asks for God's forgiveness as he orders the attack on Russia.
Around the world, unsuspecting citizens look skyward as civilization comes to a tragic end.