Amongst the Clan cats, alliances of the formal sort are rare, while occasionally, informal alliances that do not result in a name change occur. Only in very extreme situations do formal alliances, resulting in a temporary change to the Clan name, happen.
In the Super Edition Arc
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In the The Prophecies Begin Arc
- A ThunderClan patrol and a group of ShadowClan cats ally together to drive out ShadowClan's tyrannical leader, Brokenstar, and his closest warriors, and to rescue Frostfur's kits, who were stolen by Clawface. The cats that allied during this attack were: Firepaw, Graypaw, Yellowfang, a small ThunderClan patrol (led by Whitestorm), and a small group of ShadowClan elders including Ashfur, Nightpelt and Dawncloud.
- Since ShadowClan drove WindClan out, ShadowClan and RiverClan have been hunting in WindClan's territory. As a fight for hunting rights, ShadowClan and RiverClan form an alliance against WindClan, when WindClan returns to their old territory, since they had been driven out by ShadowClan's former leader, Brokenstar. Both ShadowClan and RiverClan try to chase WindClan out again, but ThunderClan becomes allies with WindClan, and together, they defeat ShadowClan and RiverClan.
- ShadowClan and WindClan form an alliance against ThunderClan, after they learn that ThunderClan is sheltering Brokentail. The two Clans form an alliance and decide to try to kill him themselves, since he had done serious harm to both of them, and ThunderClan is forced to fight back alone. RiverClan helps later on. Then they drive out the attacking Clans, bravely, and chase them out of ThunderClan territory.
- Tigerclaw of ThunderClan allies himself with Brokentail and some of his rogues, and attack ThunderClan's camp. A RiverClan patrol comes to ask about Graystripe and Silverstream's kits, but find ThunderClan fighting Brokentail's rogues. They aid ThunderClan in driving off the rogues, and the two Clans are victorious.
- When the ThunderClan camp catches fire, the ThunderClan cats travel across the river to RiverClan territory, and ask for shelter. RiverClan agrees, and the ThunderClan cats stay there until the fire stops. However, some cats, including Yellowfang, Halftail, and Patchpelt of ThunderClan breathe too much smoke and die in the fire.
- At the first Gathering mentioned in the book, Tigerstar arrives with a proposal that all Clans should ally, or become one Clan known as TigerClan. Since Firestar and Tallstar refuse, TigerClan is officially an alliance between RiverClan and ShadowClan. Later, it is revealed that BloodClan was offered a share of the forest in exchange for their help in persuading WindClan and ThunderClan to join TigerClan. Tigerstar announces that TigerClan are allied with BloodClan and that when all the four forest Clans join together with TigerClan, TigerClan and BloodClan will rule together. When Tigerstar is killed by the BloodClan leader, Scourge, all four forest Clans ally themselves under LionClan and drive BloodClan out of the forest.
- ShadowClan and RiverClan form an alliance, and make a Clan, called TigerClan. Tigerstar, the leader of the newly formed Clan, offers Firestar, ThunderClan's leader, and Tallstar, WindClan's leader, a chance to join TigerClan, but both leaders refuse.
- Later, TigerClan attacks the WindClan camp, shortly after Tallstar's refusal to join, slaughtering Onewhisker's apprentice, Gorsepaw, and weakening all the WindClan warriors, so as to teach them a lesson.
- Firestar and Graystripe travel to TigerClan, along with their close friend, Ravenpaw, to see if they are keeping half-Clan prisoners. The trio rescues the prisoners, Stormpaw, Featherpaw, and Mistyfoot, but are unable to save Mistyfoot's brother, Stonefur, who was fighting to protect the other three, is killed by Blackfoot. After Tigerstar is slaughtered by Scourge, Leopardstar is left to lead TigerClan alone. When she is asked to join the newly formed LionClan, she replies saying she will have to think about it or she'll just lead her Clan away. She leads TigerClan to the battle against BloodClan, handing it over to Firestar making TigerClan a part of LionClan.
- Before BloodClan came to the forest, LionClan only consisted of ThunderClan and WindClan, and was lead by Firestar. But after BloodClan comes to the forest, ShadowClan and RiverClan join, or at the time, TigerClan joined. Ravenpaw and Barley join LionClan as well, for the time being.
- Later, LionClan fights against BloodClan, despite how greatly they're outnumbered. Whitestorm, ThunderClan's deputy, is killed during the battle, along with BloodClan's deputy, Bone, and their leader, Scourge, who was killed by Firestar; and as soon as BloodClan learns their leader is dead, they retreat, giving victory to LionClan.
In the New Prophecy Arc
- StarClan warriors decide on four chosen cats who travel to the sun-drown-place and listen to Midnight. The chosen cats are Brambleclaw of ThunderClan, Feathertail of RiverClan, Tawnypelt of ShadowClan, and Crowpaw of WindClan. Squirrelpaw, a nosy apprentice, also comes with Brambleclaw, and Stormfur, Feathertail's brother, comes with Feathertail.
- The chosen cats, along with Squirrelpaw and Stormfur, are on their way home, and meet the Tribe of Rushing Water. The Tribe captures Stormfur, and says that he must defeat Sharptooth, a lion-cat who has been killing cats of the Tribe. After the Clan cats rescue Stormfur, they come back to the Tribe, and tell them that they will help. They give Sharptooth prey stuffed with deathberries, but Sharptooth doesn't fall for the trick. Feathertail saves Crowpaw and the Tribe by dislodging a rock at the top of the Tribes' cave, and kills Sharptooth, saving the Tribe.
- The four Clans join together as one and make the Great Journey. However, they do not take on one name, choosing to keep their own names, ThunderClan, WindClan, RiverClan, and ShadowClan. During the devastating attack on the ShadowClan camp, Twolegs start tearing down trees in ShadowClan territory. ThunderClan and WindClan ally and come to help, and Firestar loses a life from being crushed by a tree. This eventually convinces all four leaders that the Clans must leave the forest, and they set out. Finally, RiverClan allied at the end, and agrees to join the other Clans on the Great Journey. Many cats from different Clans make friends with other Clans' cats, and are sad when the Clans move into their new homes and separate.
- At his new home, in his dying breath, Tallstar proclaims Onewhisker deputy, so as to prevent the former deputy, Mudclaw, from becoming WindClan's leader, because Tallstar thought that he would lead WindClan into unnecessary battles. Later, after Tallstar dies, Mudclaw, greatly angered at his dead leader's decision, Hawkfrost, a RiverClan warrior, and other cats from ShadowClan, WindClan, and RiverClan, form an alliance against Onewhisker, saying that they don't believe he was the rightful leader of WindClan.
- ThunderClan, however, joins forces with WindClan, and fights off Mudclaw and his followers. But despite this, some of the fleeing cats take the battle to the ThunderClan camp, while Mudclaw and Hawkfrost take it to the lake, and RiverClan territory. In the end, Onewhisker emerges victorious and Mudclaw is killed by a falling tree, paving a way to the island for Gatherings.
- During the fight with the badgers, who want to take revenge on the Clans for driving them out, several cats are wounded and Cinderpelt dies while protecting Sorreltail, who is kitting. ThunderClan are saved by WindClan warriors, who heard about the attack from Midnight and came to help. Tornear and Webfoot are some of the cats sent by Onestar to help fight the badgers, and Crowfeather and Leafpool return to the lake to help. They drive the badgers off, and Firestar thanks the WindClan cats, who say that they can't let one Clan be driven out.
In the Power of Three Arc
- WindClan attacks ThunderClan, saying that they can't tolerate non-pure blood and ThunderClan's obsession with bossing the other Clans around anymore. RiverClan comes to help WindClan, because Leopardstar agrees with WindClan that ThunderClan keeps acting like the best Clan. ThunderClan asks ShadowClan for help, and Blackstar agrees, saying that there must always be four Clans around the lake, and that ThunderClan can't be driven out. He sends some warriors to help ThunderClan, and all four Clans fight until an eclipse happens, and breaks up the fight.
- Leopardstar, Blackstar, and Onestar all go to the ThunderClan camp when they find out that ThunderClan is holding Sol prisoner, saying that they don't want them near their territories even if he is contained, after all the bad things he has done. They say that if he isn't gone by the next Gathering then they will make him leave themselves.
In the Omen of the Stars Arc
- The four Clans decide to each contribute two cats to travel to the place where beavers are blocking the streams and causing the lake to dry up. The eight cats are Lionblaze and Dovepaw from ThunderClan, Petalfur and Rippletail from RiverClan, Whitetail and Sedgewhisker from WindClan, and Toadfoot and Tigerheart from ShadowClan. They fight the beavers, and Rippletail dies. They get help from some kittypets, and dislodge the dam that was blocking the water.
- Due to the rising threat from the The Dark Forest, the four Clan leaders - Firestar, Mistystar, Blackstar, and Onestar agree to set aside Clan differences so they can unite as one in order to defeat the Dark Forest. Each Clan assigns patrols to journey to another Clan's camp and aid them in the battle.
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In the Field Guide Arc
- Graystripe narrates the battle against the foxes. He represents ThunderClan at a Gathering while Firestar and Sandstorm are away rebuilding SkyClan. The Gathering is held at Snakerocks since foxes have made their dens at Fourtrees. The other Clans are nervous about being so far into ThunderClan territory. In response to that, Graystripe has an idea about driving the foxes out. The cats agree to attack when the foxes are focused on hunting or something of that nature since foxes are most aggressive when they are in their dens, guarding their kits. They will use each Clan's strengths to drive them out together and Graystripe would lead them into a battle for their homes. Cloudtail leads the patrol consisting of Graystripe, Mousefur, her apprentice Spiderpaw, and Brightheart with her keen nose. She leads the foxes to the ShadowClan ambush. Then Graystripe joins Mistyfoot and RiverClan and his patrol distracts the four foxes while WindClan attack the dens. The ambush traps the foxes. Blackstar and Graystripe order the foxes to leave and never come back and they retreat.