At the advent of a more aggressive Persian Gulf policy on the part of Iran during the interwar years, the resilience of these symbols was watched like a kind of barometer that attested to Britain’s levell of commitment to the maintenance of security in the Persian Gulf.  Britainäs abstention from the use of force against Iran, dictated by its will to protect its interests in Iran, was at times perceived as weakness by the shaykhs and merchants of the Arabian littoral.  During the period of heightened tension that accompanied Reza Shah’s rise, a perpetual cause of excitement among the Arabs inhabiting the southern littoral was the persistence of rumors that Iran would soon effect the complete withdrawal of the British from the area of the Persian Gulf waterway.

That is from the very useful The Origins of the Arab-Iranian Conflict: Nationalism and Sovereignty in the Gulf between the World Wars, by Chelsi Mueller.

By the way, on the eve of WWI, the population of Dubai was about 2,075 people, and about 500 of them were Iranian merchants.