One of the most destructive conflicts in human history , it resulted in Causation eight million fatalities not only from military engagements but also from violence , famine , and plague .

After the failed Fifth Siege of Gibraltar in 1349–50 , which ended Process_end with the death of King Alfonso XI of Castile from bubonic plague , the Kingdom of Castile was preoccupied with the Castilian Civil War and its aftermath .

During the siege , Hannibal and a large number of Carthaginian soldiers perished Death from the plague , and the survivors were in dire straits after the Greeks managed Control to cut their supply lines .

The siege lasted for four months , during which time one-third of the Portuguese troops either died Death ( mainly from the plague ) or deserted .

Taking advantage of this failure , D. Luis de Haro , invaded Attack Portugal and besieged Elvas , the main defensive system of Portugal - where the Portuguese army that had besieged Besieging Badajoz took Creating refuge and was suffering Bodily_harm a second catastrophic plague .

In the New Year of 1350 , however , bubonic plague – the Black Death – broke out Process_start in the Castilian camp .

Alfonso refused Agree_or_refuse_to_act to abandon GiveUp the siege but fell victim to the plague on 27 March 1350 , becoming Becoming the only monarch to die Death of the disease .

The war Hostile_encounter resulted in Causation famine Catastrophe , which was worsened Influence by an outbreak of bubonic plague Catastrophe .