Upon his accession to the throne, Trajan prepared and launched a carefully planned military invasion in Dacia, a region north of the lower Danube whose inhabitants the Dacians had long been an opponent to Rome. In 101, Trajan personally crossed the Danube and defeated the armies of the Dacian king Decebalus at the Battle of Tapae.
Gaius Marius was a Roman general and statesman. Victor of the Cimbric and Jugurthine wars, he held the office of consul an unprecedented seven times during his career. He was also noted for his important reforms of Roman armies.
The Battle of Vercellae, or Battle of the Raudine Plain, was fought on 30 July 101 BC on a plain near Vercellae in Gallia Cisalpina. A Germanic-Celtic confederation under the command of the Cimbric king Boiorix was defeated by a Roman army under the joint command of the consul Gaius Marius and the proconsul Quintus Lutatius Catulus.