MeanwhileintheMexicanpartoftheviceroyaltyofNewSpainthecryofindependenceraisedbyMorelosandhisbandsofIndianfollowershadbeenstifledbythecaptureandexecutionoftheleader。Butthecauseofindependencewasnotdeadevenifitsachievementwastobeentrustedtootherhands。EagertoemulatetheexampleoftheirbrethreninSouthAmerica，smallpartiesofSpaniardsandCreolesfoughttooverturnthedespoticruleofFerdinandVII，onlytoencounterdefeatfromtheroyalists。ThencametheRevolutionof1820inthemothercountry。Forthwithdemandswereheardforarecognitionoftheliberalregime。
Fearfulofbeingdisplacedfrompower，theviceroywiththesupportoftheclergyandaristocracyorderedAgustindeIturbide，aCreoleofficerwhohadbeenanactiveroyalist，toquellaninsurrectioninthesouthernpartofthecountry。
Thechoiceofthissoldierwasunfortunate。Personallyambitiousandcherishinginsecretthethoughtofindependence，Iturbide，faithlesstohistrust，enteredintonegotiationswiththeinsurgentswhichculminatedFebruary24，1821，inwhatwascalledthe\"PlanofIguala。\"Itcontainedthreemainprovisions，or\"guarantees，\"astheyweretermed：themaintenanceoftheCatholicreligiontotheexclusionofallothers;theestablishmentofaconstitutionalmonarchyseparatefromSpainandruledbyFerdinandhimself，or，ifhedeclinedthehonor，bysomeotherEuropeanprince;andtheunionofMexicansandSpaniardswithoutdistinctionofcasteorprivilege。Atemporarygovernmentalso，intheformofajuntapresidedoverbytheviceroy，wastobecreated;andprovisionwasmadefortheorganizationofan\"ArmyoftheThreeGuarantees。\"
Despiteoppositionfromtheroyalists，theplanwonincreasingfavor。Powerlesstothwartitandinclinedbesidestoapolicyofconciliation，thenewviceroy，JuanO’Donoju，agreedtoratifyitoncondition——inobediencetoasuggestionfromIturbide——thatthepartiesconcernedshouldbeatliberty，iftheydesired，tochooseanyoneasemperor，whetherhewereofareigningfamilyornot。Thereupon，onthe28thofSeptember，theprovisionalgovernmentinstalledatthecityofMexicoannouncedtheconsummationofan\"enterpriserenderedeternallymemorable，whichageniusbeyondalladmirationandeulogy，loveandgloryofhiscountry，beganatIguala，prosecutedandcarriedintoeffect，overcomingobstaclesalmostinsuparable\"——anddeclaredtheindependenceofa\"MexicanEmpire。\"TheactwasfollowedbytheappointmentofaregencytogovernuntiltheaccessionofFerdinandVII，orsomeotherpersonage，totheimperialthrone。
OfthisbodyIturbideassumedthepresidency，whichcarriedwithitthepowersofcommanderinchiefandasalaryof120，000