When Data was commanding the USS Sutherland, he was still wearing his engineering (yellow) uniform. As the ship's captain, he should have been wearing a command (red) uniform.
Near the close of "Part I", Worf resigns his commission as a Starfleet officer. However, at the end of this episode, he simply requests permission from Picard to return to duty, which Picard grants. Presumably, it should be far more difficult to return to duty after resigning one's commission.
As was common on many episodes of TNG, Chief O'Brien is mistakenly shown wearing lieutenant's pips.
Sela says that the Federation fleet consists of exactly 23 starships, however both Federation and Romulan computer displays show no more than 17 vessels in the fleet.
The Federation puts out a tachyon net to track the Romulan Ships. However, this net cannot extend infinitely into space. Why don't the Romulan ships just cloak and go around the net? Also, if the ships are ten million kilometers apart, the net has gaps big enough for a fleet of ships to fly through.
The ships form a line to create a sort of dragnet, hoping to detect any cloaked ships which attempt to cross it. Picard, and Sela, seem to forget that space is 3 dimensional. They could easily go above or below it.
In the fight in the beginning, Worf reports that "aft shields are gone." In the very next scene, the two Klingon ships attacking them fire and the ship Worf is on absorbs the shots with its aft shielding.
In the fight in the beginning, a Klingon reports that the ship is entering the chromosphere. While the later scene involving the ship destroying the two behind it does appear to be close to the star, the scene in which that is reported shows the star well away on the viewscreen.
Picard's chair in his ready room is a different chair in this episode from that used in the rest of the series.
Worf gave no reaction when he saw Sela on the viewscreen in Lursa and B'Etor's quarters. Given that he worked closely with Tasha and had no prior knowledge of Sela's existence he should have given some sort of reaction.
Riker: Nicely done. I sure hope we know what we're doing.
Picard: As do I, Number One.
Larg: May you die well.
Kurn: You and I will fight battles that others can only dream of. The time for glory is here. It is not a time to worry about stabilizers! It is a time to celebrate! For tomorrow we all may die!
Worf: You drink with our enemies?
Kurn: How many are Gowron's men? How many Duras's? Does it matter? When we meet in battle, we fight to the death, but here, here we're all warriors! All Klingons!
Kurn: What's wrong? Kill him!
Kurn: But it is our way. It's the Klingon way.
Worf: I know. But it is not my way.
Larg: You are lucky, Kurn, but luck always runs out. Someday I will stand over your broken corpse and drink to the victory of the Duras!
Kurn: Celebrate, for tomorrow we all may die!
Lt. Cdr. Hobson: I'd like to request a transfer... I don't think I'll make a good first officer for you... I don't believe that an android is a particularly good choice for captain.
Data: I understand the reasons for your concern. Request denied.
Sela gave Picard 20 hours to withdraw, which is close to one Romulan day.
The Nebula-class starship appears again in this episode, and has been slightly modified, as the Sutherland is noticably different from the Phoenix. This is most notable in the "dish" on the back of model; the Sutherland has a more triangular "dish" than the round dish of the Phoenix.
Robert O'Reilly and Jordan Lund would later be reunited in the Star Trek: Enterprise episode "Bounty."