UGM-96 Trident I

The UGM-96 Trident I, or Trident C4, was an American submarine-launched [ballistic missile], built by Lockheed Martin [Space Systems] in Sunnyvale, California. First deployed in 1979, the Trident I replaced the Poseidon missile. The Trident was intended to have longer range than the Poseidon, allowing the fleet to maintain a longer distance from the target, enhancing survivability. It was retired in 2005, having been replaced by the Trident II.
The missile was a three-stage, solid-fueled system, capable of carrying up to eight W76 warheads in the Mark 4 RB.
Twelve - and s were retrofitted with Trident I missiles, which replaced older Poseidon missiles. The first eight s were armed with Trident I missiles. The Ohio-class submarines were designed for the Trident II missiles, but used Trident I missiles until the Trident II missiles became available.
In 1980, the Royal Navy requested Trident I missiles under the Polaris [Sales Agreement]. In 1982, the agreement was changed to supply Trident II instead.