The economy of Republican Spain was so bad, inflation had reached 300%. Food and raw material was hard to come by, meaning the war effort could not be as efficiently supported.

 
Better foreign relations with countries that are seeing nationalism and fascism on the rise, which leads to more foreign aid in terms of food, armament and materiel.

 
Political unity (e.g. the unification of the Carlists and the Falange) made it easier for Franco to develop a centralized command structure for the military

 
The military, alongside some foreign fighters (e.g. Condor Legion) were battle-scarred and combat hardened veterans.

 
The Nationalists controlled the agricultural areas in the south form the outset. This meant that Franco's troops were better fed compared to Republican troops

 
Franco had control over the Moroccan regular army troops, the German Condor Legion, Italian Aviazione Legionaria Portugese supply of ammunition volunteers of the Spanish Legion, Irish, British and American volunteer troops.

 
Republican failure to hold strategic locations (e.g. Madrid) and its failure to recapture these strategically valuble areas (e.g. Ebro offensive)

 
In Republican controlled areas, public utilities, transport, industries and farms were controlled by the Anarchists, which meant that the Republicans could not properly supply its war effort.

 
Strong ties with Nazi Germany and Fascist Italia meant better military aid and support, unlike the Republicans, where the USSR made them pay for tanks and aircraft using all of the gold in reserve.