Why was Archduke Franz Ferdinand of Austria-Hungary a key player in World War I? He ordered an attack on Serbia.
He was assassinated by a Serbian nationalist.
He created an alliance with Great Britain.
He authorized the use of poison gas on Russia.

He was assassinated by a Serbian nationalist.

Explanation:

Archduke Franz Ferdinand of Austria-Hungary was an instrumental key figure in World War 1 because it was his assassination in Sarajevo on June 28, 1914 by a Serbian nationalist that caused the declaration of war between Austria and Serbia.

Until his death, he was heir to the throne in Austria.

the bar kochba rebellion (132-135) against the roman empire, also known as the second jewish-roman war, was the second major jewish revolt in judea and the last of the great jewish-roman wars.

after the first jewish-roman war of the years 66-73, the roman authorities took measures to crush any new attempt of rebellion in judea. his political situation was modified and instead of a prefect a governor of praetorian rank was appointed, and in the ruins of jerusalem the seat of a complete roman legion, the legio x fretensis was established.

the political and religious direction of the jewish people was left in the hands of the sanhedrin, with initial headquarters in yavne.

the direct causes of the rebellion vary according to the source. the roman historian dio cassius (155-229) attributes the revolt to the decision of hadrian to found in the place of jerusalem a roman city called aelia capitolina (aelia by its own name and capitolina in honor of the roman god jupiter). on the other hand, the jewish sources, while recognizing this resolution as true, assign higher priority to the decrees dictated by hadrian that forbade the brit milah (circumcision), the respect of the sabbath and the laws of purity in the family.

hadrian's intention was to "civilize" and incorporate the jews once and for all into the greco-roman culture. for greek and roman culture, circumcision was an intolerable mutilation.

the jewish tradition tells in the midrash tanjuma a meeting between rabbi akiva and the governor turnus rufus, where he asked for an explanation about the circumcision.

an additional legion, the legio vi ferrata, moved to the province to maintain order, and work began in the year 131 after the governor of judea, turnus rufus performed the founding ceremony of aelia capitolina. a roman coin with the inscription aelia capitolina was struck in the year 132.

the tannaim rabbi akiva, who without being named nasi directed the sanhedrin, convinced the other members to support the imminent rebellion.

the jewish leaders carefully planned the second rebellion to avoid the numerous errors that had been committed in the first one. in the year 132 the rebellion led by bar kochba quickly expanded from modiim throughout the country, defeating the x roman legion based in jerusalem and destroying the xxii roman legion that had come from egypt.