Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
This mass of troops however was only destined in part for the
expedition to Italy. Some 20,000 men were sent to Africa, the smaller
portion of them proceeding to the capital and the Phoenician territory
proper, the majority to the western point of Africa. For the
protection of Spain 12,000 infantry, 2500 cavalry, and nearly the half
of the elephants were left behind, in addition to the fleet stationed
there; the chief command and the government of Spain were entrusted
to Hannibal's younger brother Hasdrubal.
The immediate territory of
Carthage was comparatively weakly garrisoned, because the capital
afforded in case of need sufficient resources; in like manner a
moderate number of infantry sufficed for the present in Spain, where
new levies could be procured with ease, whereas a comparatively large
proportion of the arms specially African--horses and elephants--was
retained there.
The chief care was bestowed in securing the
communications between Spain and Africa: with that view the fleet
remained in Spain, and western Africa was guarded by a very strong
body of troops.