The Psi Corps and President Clark, whose government has discovered Shadow vessels buried in Earth's solar system, begin to harness the vessels' advanced technology. The Clark administration continues to become increasingly xenophobic and totalitarian, and uses a military incident as an excuse to declare martial law. This triggers a war of independence on Mars, which had long had a strained political relationship with Earth. Babylon 5 also declares independence from Earth, along with several other outlying Earth Alliance colonies. In response, the Earth Alliance attempts to retake Babylon 5 by force, but with the aid of the Minbari, who have allied with the station against the growing Shadow threat, the attack is repelled.
Becoming concerned over the Shadows' growing influence amongst his people, Centauri ambassador Londo Mollari attempts to sever ties with them. Mr. Morden, the Shadows' human representative, tricks him into restoring the partnership by engineering the murder of Mollari's mistress while putting the blame on a rival Centauri House. Open warfare breaks out between the Shadows and the alliance led by Babylon 5 and the Minbari. It is learned that genetic manipulation by the Vorlons is the source of human telepathy, as it is later discovered that Shadow ships are vulnerable to telepathic attacks. Displeased at the Vorlons' lack of direct action against the Shadows, Captain John Sheridan browbeats Vorlon ambassador Kosh Naranek into launching an attack against their mutual enemy. Kosh's deeds lead to his subsequent assassination by the Shadows.
Former station commander Jeffrey Sinclair returns to Babylon 5 to enlist the aid of Captain Sheridan, Delenn, Ivanova and Marcus in stealing the Babylon 4 space station and sending it 1,000 years back in time to use it as a base of operations against the Shadows in the previous Minbari-Shadow war. Undergoing the same transformation as Delenn at the end of Season 1, Sinclair transforms into a Minbari and is subsequently revealed to be the actual Valen of Minbari legend, rather than a reincarnation. Spurred by the reappearance of his assumed-dead wife (who now works for the Shadows), Sheridan travels to Z'ha'dum, the Shadow homeworld, in an attempt by them to recruit him. However he instead destroys their largest city in a kamikaze nuclear attack, and is last seen jumping into a miles-deep pit to escape the explosion. Garibaldi, during a fight with Shadow vessels, goes missing.
在《复仇者联盟4：终局之战》的结尾，美国队长将盾牌交给了猎鹰（安东尼·麦凯饰），相信他能够继承美国队长的精神。此后，“猎鹰”萨姆·威尔逊和“冬兵”巴奇·巴恩斯（塞巴斯蒂安·斯坦饰）联合参与了一场全球性冒险行动，他们的能力和耐心受到考验 [39]。“美国队长”史蒂夫·罗杰斯卸任、灭霸被终结后，这个世界依旧不宁静。猎鹰继承了美国队长头衔之后美国政府对此心存抵触 [22]。“泽莫男爵”赫尔穆特·泽莫（丹尼尔·布鲁赫饰）似乎还要捣乱，猎鹰与冬兵出任务时还遇到了美国队长的前女友莎伦·卡特（艾米丽·万凯普饰） [1
