Once they have resolved to go to war, a fetial returns to the enemy frontier carrying a javelin with a steel or fire-hardened tip and dipped in blood.
The fetial is connected to matters of law and not directly to war, hence in his formulae he never invokes Mars, but Jupiter, Juno, Janus or Quirinus.
The religious relevance of the collegium or sodalitas lay in ensuring that Rome enjoyed the protection of gods in its relationships with foreign states.
When this period of time had expired he went back to the border and opened the hostilities with a magic gesture: while affirming once again the good right of Rome he threw a spear with steel point or a javelin of corniolum hardened with fire into the enemy's territory.
[11] According to G. Dumézil, the initial contract concluded with the gods and extended through the sacra and the signa is sufficient to justify the acts of official religious authorities (such as pontiffs and augurs) within the Roman ager.
They rely on a set of ceremonies that bestow a religious value on the political or military decisions of the magistrates, ensuring that under any circumstance Rome has the gods on her side.
The god under whose protection they act and whom the pater patratus invokes is Iupiter Lapis in the rite of the conclusion of a treaty[12] and in general when there an agreement is reached.
[13] The author of Cicero's apocryphal speech of Furius Filus and the Christian apologists blamed the Romans for craftily using the ius fetiale in order to ensure divine support for Rome in international disputes.
They allege that Romans were not moved by a desire for justice in their use of the ius fetiale, but rather bent its rules and made a disproportionately excessive use of its technicalities to acquire an undue advantage over other peoples with the ultimate goal of stealing their lands and riches.