Londonattack:howEuropehasovercometerrorcampaignsbeforeAmidawaveofIslamist-inspiredterrorattacks,itiseasytoforgetthatEuropehasbeenthroughsimilartormentsinthepastandemerged,peacerestored,withitsdemocraticinstitutionsintact.MARCH23,2017PARIS—Arentalcarandakitchenknife.Thatwasallittook–asidefromhiswillingnesstodieforacause–forasuspectedIslamistassailanttospreaddeathandterrorincentralLondonyesterday.TheattackoutsidetheHousesofParliament,whichleftfourpeopledeadanddozensinjured,wasthelatestinastringoflow-tech,high-profileterroristincidentsinEurope.And,frankly,thereisnotmuchthatauthoritiescandoatstreetleveltostopthem.Goodpoliceandintelligenceworkcanheadoffsuchincidentsandsavelives,asEurope’srecenthistoryhasshown.Thegraverthreat–thatterroristattacksundermineWesternsocietiesbyspurringanti-Muslimhatredanddivisions–isharder,thoughnotimpossible,toconfront.YetinthefaceofthecontemporarywaveofIslamist-inspiredterrorattacks,itiseasytoforgetthatEuropehasbeenthroughsimilartormentsinthepastandemerged,peacerestored,withitsdemocraticinstitutionsintact.Wednesday’sattackrecalledsimilarrecentincidents.LastyearamandroveaheavytruckthroughcrowdscelebratingBastilleDay,theJuly14nationalholiday,inthesouthernFrenchcityofNice,killing86people.InDecember,aTunisianfailedasylum-seekerdroveatruckintoaChristmasmarket,killing12.ButtwoothereventsthisweekalsorecallmoredistantterrorcampaignsinEurope,andserveasareminderthattheycanbeovercome.InNorthernIreland,formerIrishRepublicanArmychiefMartinMcGuinnesswasburiedThursday,hiseventualroleasapeacemakerearningpraisethatoffsetsomeoftheangersparkedbyhisearlierroleinthedeathsofmorethan600civiliansatthehandsoftheIRA.AndinParis,thetrialcontinuedofCarlos“theJackal,”thenotoriousVenezuelaninternationalterroristwhowreakedviolencearoundEuropeinthe1970sand'80s.IlyichRamirezSanchez–hisrealname–isalreadyservingconsecutivelifesentencesinFranceforothercrimes,butisnowalsofacingchargesrelatingtoagrenadeexplosioninaParisshoppingarcadein1974thatkilledtwopeople.InItaly,theRedBrigadesspearheadedaspateofmurdersandkidnappings–mostnotablyofformerPrimeMinisterAldoMoro–duringthe“yearsoflead”inthe1970sand'80s.InGermany,theBaader-Meinhofgroupwasactivefornearlythreedecades,thoughittendedtochooseagentsofthestateandUSservicemenasassassinationtargets(includinga1979attemptonthelifeofformerNATOchiefGen.AlexanderHaig).“Carlos”wentontherampagetotrytowinthereleaseofhiswifeafterherarrestin1982byFrenchpolice,stagingfivebombingsinParisandelsewhereinthesubsequentmonthsthatkilled12peopleandinjuredhundreds.Andfor30yearstheIRAwagedawaragainsttheBritishstatethatusedterroristviolenceagainstcivilians,aswellasmoretraditionalguerrillatacticsaimedatthesecurityservices,untiltheGoodFridaypeaceaccordendedthefightingin1998.AllthesegroupssavetheIRA,whichdisarmedvoluntarily,weredismantledbythepolice,aidedbyinformersandinfiltratedspies.Carefulintelligencework,outofthepubliceye,eventuallyrestoredpeacetotheEuropeancontinent.Itisstepped-upsecurityworkonwhichEuropeangovernmentsarenowpinningtheirhopes.SincethemultiplebombattacksonLondoninJuly2005,theBritishsecretserviceMI5andpolicehavetightenedtheircoordinationinfivejointunitsaroundthecountry.Between10,000and15,000peopleareworkingoncounter-terrorisminBritaintoday,accordingtosecurityexperts.Theyarenotfoolproof.Yesterday’ssuspectwas“onceinvestigatedbyMI5inrelat...