The Roman Empire lost the strengths that had allowed it to exercise effective control over its Western provinces; modern historians mention factors including the effectiveness and numbers of the army, the health and numbers of the Roman population, the strength of the economy, the competence of the Emperors, the internal struggles for power, the religious changes of the period, and the efficiency of the civil administration.
Romerriget mistede sin styrke, der havde muliggjort effektiv kontrol; moderne historikere nævner faktorer inklusive effektivitet og antallet i hæren, sundhed og den romerske befolkning, økonomiens slagkraft, kejserens kompetencer, religiøse ændringer i perioden og civiladministrationens.