The UGM-133 Trident II or or Trident D5 is a submarine-launched ballistic missile (SLBM).
A few weeks after the outbreak, the USS Pennsylvania receives orders to launch one its nuclear missiles at Chicago. However, weapons officer Lieutenant Jason Riley and fellow officers Pierce and McGuire refuse the order and mutiny against Captain Renwick, unwilling to fire on their own county and people. The situation is defused when Renwick is discovered to have been bitten and acquiesces; Riley mercy kills him and takes command of the sub.
Later, Theodore Maddox plots to have his cult use the nuclear missiles stowed on the USS Pennsylvania to end the remainder of humanity on the surface of the Earth and give the human race a new beginning. To this end, the cult chases Morgan Jones who came into possession of one of the two launch keys for the Pennsylvania. Jason Riley, the sub's former Weapons Officer, is eventually able to force Morgan to give him the key. Teddy eventually reveals his plan to Alicia Clark before locking her and the people that he intends to survive in a secret Cold War-era bunker beneath the Franklin Hotel.
Teddy, Riley and Dakota board the sub where Riley works to bring the weapons systems online and Teddy reveals to Dakota that he intends to die in the coming nuclear destruction. Morgan's Group, having been warned by Alicia, boards the sub in an attempt to stop Teddy's plan, but Morgan and Victor Strand arrive too late and Teddy and Riley manage to fire off a single Trident missile before the two men capture them and prevent any more missiles from being fired. Riley reveals that the launched missile contains ten nuclear warheads which are targeted at various locations in Texas and that it can't be stopped. Teddy suggests that two of the locations may be the Texas-Mexico border and Valley Town. Morgan orders the two men to leave and, angry at Strand and blaming him for their failure, sends the other man away as well.
It's later stated that at least 8 of the warheads went off with a map owned by Morgan and Grace showing targets that were hit in both Texas and Louisiana. While driving through the devastation caused by the bombs detonating, Grace states that the warheads detonated on the ground and that it is even worse than she thought. According to Will, the only walkers that are dangerous as a result of the bombs are those that died of the radiation from the blasts and then reanimated. The walkers that merely passed through the radioactive zones are clean despite their exposure.
It's later discovered that at least one of the ten warheads was a dud, but it cracked open and is leaking radiation all over the place. It is eventually found by Sarah Rabinowitz and Josiah LaRoux by accident and then recovered by Sage and given to the Stalkers. The Stalkers subsequently weaponize a number of walkers using the radioactive material from the warhead, although it costs the lives of all of the Stalkers who handle it. Arno uses the walkers as leverage in an attempt to take over Strand's Tower, but he is foiled by Morgan's group. Later, a number of the walkers wander into Alicia's Camp and explode, rendering it uninhabitable.
When Alicia meets Paul, he reveals that his wife Rowan had died in one of the blasts. Paul had heard her death over the radio with the high-pitched whine that the blast created destroying what was left of Paul's hearing.
While traveling past one of the blast craters, Arno and Sage find it to be filled with numerous walkers. Arno guesses that the herd must've fallen in and has probably been stewing down there for months. Arno states that there's "too many" in the crater and that if one of them gets out, nobody's going anywhere.
- Dakota (Alive)
- Emma (Indirectly Caused)
- Garcia (Caused)
- Muhammad (Caused)
- Several unnamed Stalkers (Caused)
- Many unnamed Texas survivors (Caused and Direct)