Emperors, Frontiers, and Foreign Relations 187which seems to have been operated only (at best) when a Roman expedi-
tionwasinprospect,anysupplementationofthecommonstockofnotions
abouttheworldbeyondthefrontierswouldthustendtocomeeitherinthe
wakeofmilitaryoperationsorasaproductoftheceaselessdiplomatictraf-
ficofsuppliants,hostages,andembassies.ThusunderClaudiusanembassy
camefromakinginCeylonanddeliveredinformationaboutthelocation,
geography, and topographyof the island.^119 Round the fringes of the Em-
pire itself such diplomatic trafficwas intense, and its scale and importance
cannotbeexploredhere.Apartfromexamplesalreadygiven,^120 oneofthe
papyrifromDura-Europos(P. Dura60B)happenstorevealaParthianenvoy
onhiswayto(orfrom)SeverusandCaracallainabout208.SimilarlyPliny
sentontoTrajaninRomealettercarrier(tabellarius)fromkingSauromates
oftheBosporus,givinghimadiploma(apermittorequisitiontransport)on
thegroundsthatthekinghadwrittentosaythattheinformationwhichthe
mancarriedwasurgent.AnembassyfromtheBosporus,enroutesimulta-
neously,waspursuingamoreleisurelycourse.^121 Itisimportanttostressthat
therequests,accusations,self-justifications,orreportswhichflowedintothe
emperorthroughsuchdiplomatictrafficallemanatedfrominterestedparties
attemptingtogainthehelporprotectionoftheemperor.Themorequickly
theemperorfeltobligedtoact,themorelimitedwouldbethechoicesopen
tohim.IntheearlyEmpireafullexaminationofrightsandwrongsmight
involvetheconflictingparties,ortheiremissaries,travellingtoappearbefore
theemperorinRome.Soforinstancethecomplexissuesandmutualaccusa-
tionsasbetweenHerodofJudaeaandAretasofNabataea,inwhicheitheror
bothkingsmighthavebeendeposed,werefinallyresolvedinahearingbe-
foreAugustusinabout8–7b.c.atwhichNicolausofDamascusspoke.^122 By
thefourthcenturythemorecharacteristicpatternwasthedirectcontrolof
militaryanddiplomaticaffairsbytheemperorinthefield,whichhasalready
beendiscussed.
Thustheburdenofproofmustrestonthosewhowouldclaimthatem-
perorsbothcouldanddiddrawonsystematicsourcesofup-to-dateinfor-
mation from beyond the frontiers. Caracalla could write to the Senate in
about215tosaythatstrifebetweenthetwoclaimantstotheParthianthrone
wasofgreatadvantagetotheRomanstate;^123 butneitherhenorhissucces-
sors,ElagabalandSeverusAlexander,hadanymeansofanticipatingthatthe
119.NH6,84–88.- Seethesecondandtheimmediatelyprecedingsectionsabove.
- Pliny,Ep.10,63–64,67.
- Josephus,Ant.16,10,8–9(335–55).
- Dio77,12,2a–3(387).