Guild Leader can add other guilds as ally.  Open guild interface, click ally info button to open alliance interface.  Choose “Add Ally Guild”, input or paste guild name to add it.  To add a guild as an ally doesn’t need the confirmation of target guild - this is similar as adding friends.  If your ally guild sets as “guild mode”, ally guild members are the same as your guild members – won’t be hurt in battle and ally guild members’ name will be shown in blue color.  One guild can have 5 ally guilds at most.