The aforesaid passage in Tabari makes an interesting revelation. It means that when in 711-712 C.E. regular campaigns were undertaken for the conquest of Spain by Tariq b Ziyad and Musa b Naseer the Muslims were already familiar with Spain, and such familiarity helped in the process of conquest.
Another point which emerges from this account is that Uthman contemplated the conquest of Constantinople via Spain. At that time there were only two great powers in the ancient world namely the empire of Persia, and the
empire of the Byzantines. The empire of Persia was completely subjugated during the time of Uthman. Syria, Palestine, Egypt and North Africa were wrested from the Byzantines, but the Byzantines still held Constantinople, Asia Minor and some parts of Europe. It appears that Uthman contemplated the complete subjugation of the Byzantine empire as well and his strategy was to launch a two pronged attack against Constantinople one from the east via Syria and Asia Minor and the other from the west via Spain. The attack from the west envisaged the subjugation of the continent of Europe. If there had been no internal dissension within the ranks of the Muslims, Uthman was likely to have embarked on his ambitious plan of the conquest of Europe and Constantinople.
When the Muslims completely subjugated Persia during the caliphate of Uthman, and when the Muslims after conquering North Africa succeeded in getting a foothold in Spain, the Byzantines must have felt alarmed at the rising tide of the Muslims. It may also be borne in mind that Umar had forbidden the Muslims to venture across the seas, but Uthman had withdrawn that restriction. During the time of Uthman the Muslims beat the Byzantines on the sea several times. During the time of Uthman the situation had thus become very critical for the Byzantines In open warfare the Byzantines were no match for the Muslims. The Byzantines therefore encouraged schemes for the subversion of Islam from within. It appears to me that those who conspired against Uthman were really playing in the hands of the Byzantines and other foreign powers. Uthman beat the enemy on the battle ground but he could not beat them in the matter of intrigues and underhand subversive activities.