Believing that the Cardassian Union is now under the control of the Founders, the Klingon Empire declares war against Cardassia and launches a full-scale invasion of the Union's territory. The Federation condemns the invasion and the Klingons respond by backing out of the Khitomer Accords, ending the Federation-Klingon peace treaty.
The Defiant heads for Cardassian space to rendezvous with Gul Dukat and the Detapa Council. On the way, they come across a debris field consisting of several destroyed Cardassian warships. While it is possible that there could be survivors, the Defiant cannot risk dropping its cloak in case there are cloaked Klingon ships still in the area. The Defiant moves on to rendezvous with Dukat.
Dukat's ship, the Prakesh, is under attack by three Klingon Birds-of-Prey. The Defiant enters the fray and destroys one of the Klingon ships with their first volley of phaser fire.
A yellowshirt is killed when her console explodes in her face.
Worf takes control of the Defiant's tactical station and fires on another Bird-of-Prey, destroying it.
Another yellowshirt is killed just as the Defiant beams over the Cardassian survivors.
As the Klingons launch their attack on Deep Space 9, two of their ships are shown to be destroyed by the station's first salvo of photon torpedoes.
After DS9's first phaser salvo, the Klingons have lost eight ships.
Another four Klingon ships are destroyed before the Negh'Var fires directly on DS9's core section. When the core section is hit, two crewmen in Ops are killed.
When the first Klingon boarding party appears in Ops, three of the five are shot by Sisko and Kira.
Of the second boarding party, three of them are shot by Worf. A Bajoran ops officers is also killed when his console explodes.
A third boarding party appears in Ops. Sisko kills one of the Klingons and O'Brien kills two, but one of the Klingons shoots a Starfleet blueshirt.
Three Klingons on the upper level of the promenade shoot two Bajoran deputies. As they run across the walkway, a pair of deputies taking cover behind a pillar appear and shoot all three of the Klingons.
A Bajoran deputy on the promenade's upper level shoots a Klingon on the lower level. He is then blasted off the walkway by another Klingon that he missed.
Odo beats down two attacking Klingons on the doorstep of the Bajoran temple. Another Klingon raises his bat'leth to strike down the constable only to get shot in the back by Dr. Bashir.
In a corridor in the habitat ring, Gul Dukat and Garak are fighting side by side. Gul Dukat uses a bat'leth to fend off two Klingons while Garak shoots two others with his phaser. There are also several Klingons and two Starfleet guards already lying dead on the deck.
As Odo talks to Sisko over the comms, behind him another Bajoran security officer is shot by a Klingon. That Klingon is then shot by another deputy.
Sisko, Worf and Dax fight and kill several Klingons in hand-to-hand combat.
Kira and Dukat find the wreckage of an old Cardassian ship, the Ravinok, on the desert world of Dozaria. Just outside the wreck is a circle of grave mounds, twelve in all. Dukat digs up the graves to identify the remains and identifies one of them as Tora Naprem, a Bajoran he took as a mistress during the Occupation.
Kira and Dukat find the survivors of the Ravinok being held prisoner by the Breen who are using them to mine dilithium. After ambushing and possibly killing two guards and taking their suits (which occurs off-screen), they try to free the Bajoran prisoners. Kira is searching for a specific prisoner, an old friend called Lorit Akrem. Another prisoner tells Kira that Akrem died in a cave-in two years previously.
Two Breen guards run into the cave to stop Kira and Dukat but both are shot dead by Kira and one of the prisoners.
During a dogfight between the Defiant and two Jem'Hadar fighters inside the atmosphere of a gas giant, a redshirt dies when his console explodes.
Janklow - A human engineer on the Defiant portrayed by Tom Morga. He dies when an explosion occurs on Deck 2.
When the Defiant launches a probe armed with a quantum warhead, one of the Jem'Hadar ships detects it and opens fire on the Defiant, causing heavy damage. Two of the minor bridge crew - Boyce and Peterson - are killed, but the quantum probe turns around and homes in on the Jem'Hadar ship, destroying it.
The Engineering crew deploy a probe to lure in the second Jem'Hadar ship and reconfigure the Defiant's main deflector into a phaser emitter. When the Jem'Hadar move in, Worf fires on them with the deflector phaser and destroys them.
When Dax, Worf and Kor find the legendary Sword of Kahless, they are followed by Toral of the House of Duras. Toral demands that Kor hand over the sword and Kor uses the ancient bat'leth to kill one of Toral's henchmen.
Dax uses a phaser to kill a large, spined cave-rat that she, Worf and Kor eat. Kor unceremoniously uses the Sword of Kahless as a dinner utensil.
Toward the end of the episode, Toral and his warriors catch up to Dax and the others. With Worf using his mek'leth and Kor the Sword of Kahless, they kill the rest of Toral's men. Toral himself is left alive.
In the episode's teaser, Sisko shows his senior staff a recording of a bombing that took place on Earth at a diplomatic conference between the Federation and the Romulan Empire. 27 people were present and all were killed in the blast. A magnification of the recording shows a piece of pottery melting into a luminescent bronze-coloured liquid just before the explosion, indicating that changelings have infiltrated Earth.
Near the end of the episode, the Defiant goes into battle against another Starfleet vessel, the USS Lakota. After the battle, Worf informs Captain Sisko on Earth that two crew members, Bartlett and Ramsey, are dead. The Lakota supposedly suffered 24 casualties before standing down.
Gul Dukat escorts Major Kira to a conference aboard his new ship, the freighter Groumall. When the vessel arrives at Korma, they find that the entire outpost has been destroyed and there are no survivors. A Klingon Bird-of-Prey decloaks moments later which was responsible for destroying the outpost.
The Groumall plays possum and lures the Klingons into a trap by making them believe that the freighter is carrying valuable cargo. When the Klingon Bird-of-Prey tractors the Groumall, Kira fires a salvaged planetary disruptor upon the Klingon ship and disables it.
After disabling the Klingon ship, Kira, Dukat and the Cardassian crew beam aboard the Bird-of-Prey. As soon as they beam in, Kira and Dukat shoot two of the Klingons.
A fight ensues in the Bird-of-Prey's weapons room and Kira kicks a Klingon into a ruptured conduit. As soon as the Klingon touches the conduit, he is vaporized.
By hacking the Klingons' transporter codes, Kira beams Dukat's whole crew over to the Bird-of-Prey and beams all of the Klingons to the Groumall. Dukat then decides to obliterate the Groumall and its new Klingon crew by firing the disruptors upon it.
Worf's brother Kurn saves his life when the pair of them infiltrate a damaged Klingon ship. Worf lies to a lieutenant aboard the ship but the lieutenant suspects the two of them are saboteurs. He draws a knife while Worf's back is turned, but Kurn notices the knife and draws his disruptor pistol, shooting the lieutenant.
In this episode, Worf faces a hearing regarding his involvement in the destruction of a civilian Klingon ship. At the beginning of the episode, he wakes from a nightmare where he is surrounded by dead Starfleet crewmen and Klingon children.
The civilian transport that the Defiant inadvertantly destroyed was carrying over 400 passengers.
When the Alliance attacks Terok Nor, one of the attacking Birds-of-Prey is destroyed by the station's weapons.
Smiley pilots the new Terran version of the Defiant under the prime Captain Sisko's command and together they destroy two Klingon ships attacking the station.
The Defiant attacks Regent Worf's flagship, which is massive in comparison. Sisko takes the helm and uses the Defiant's small size to his advantage and lands several precision strikes on the Negh'Var. Some of Worf's bridge crew are killed when their consoles explode.
A Bird-of-Prey flies in to take out the Defiant but is suddenly destroyed when Bashir arrives with his raider.
Sisko and Bashir manage to destroy most of the Negh'Var's disruptor turrets and cause major damage. By the time Worf decides to retreat, the last of his bridge crew have been killed by collapsing bulkheads.
At the start of the episode, the Defiant returns to DS9 to find that the station has suffered an attack. One of the upper docking pylons has been destroyed and there are almost 200 casualties, though only 18 are confirmed dead.
When the Defiant crew and Weyoun's unit of Jem'Hadar arrive at Vandros IV, they beam down to discover that a dampening field has rendered their phasers useless. They are forced to engage the Jem'Hadar renegades in brutal hand-to-hand combat that results in many deaths on both sides.
The Starfleet crew and their Jem'Hadar allies breach the renegades' compound, slaying the renegades with kar'takin swords.
The renegades' stronghold and the Iconian gateway are destroyed when the Defiant crew plant a bomb inside the structure. It is unknown if any renegade Jem'Hadar survived the detonation.
Omet'iklan and his surviving Jem'Hadar troops remain on Vadros IV to eliminate the remaining renegades.
Dr. Bashir and Dax arrive on the Teplan homeworld to find that their society has been reduced to a pre-industrial state following the introduction of a Dominion bio-weapon. One of the first things they see after beaming down is a Teplan man carting away dead bodies.
Tamar - A Teplan portrayed by Alan Echeverria. He was a victim of the Blight who came to the healer Trevean when the disease quickened in him. Trevean gave Tamar a poisonous herbal concoction that killed him swiftly so he would not need to endure the lingering pain of the Blight.
Dr. Bashir tries to devise a cure for the Blight and several quickened patients volunteer to help him. Unfortunately, exposure to the EM fields given off by the doctor's instruments cause the virus to mutate and the patients all experience tremendous, agonizing pain. Trevean enters Julian's makeshift clinic and gives a patient his "remedy", causing her to die quickly. The other suffering patients then call out to Trevean to take away their pain and they are all given the poison.