What is an example of irony in the opening chapters of the novel, Killers of the Dawn?

When the group is down in the tunnels, the Vampaneze allow them time to get out of the tunnels and save themselves. This is ironic since these two groups are at war. If the Vampaneze are able to kill the group that has been sent to capture their Lord, they will have an advantage in the war. This action foreshadows that there is another reason as to why the Vampaneze have allowed the group a head start.