Circe tells Odysseus that he and his crew will have to pass "the island of the Sirens / those creatures who spellbind any man alive." After this, he has somewhat of a choice: once his ship makes it through the Clashing Rocks, he must either steer closer to Scylla, a six-headed man-eating monster, or Charybdis, a huge whirlpool. Scylla will, almost certainly, eat six of his men; however, Charybdis could drown the entire crew, captain and all. Odysseus asks Circe if he cannot simply fight off Scylla and avoid Charybdis, thereby saving all, but she assures him that there is "'no fighting her, no defense.'" After this, Odysseus and his men will come to the island of Thrinacia, where the Sun god keeps his sacred cattle. If the men do anything to harm the cows, his entire crew will perish, and he will, at best, "'come [home] a broken man.'"
The next morning, Odysseus and his crew set out. He tells them,
"Friends...it's wrong for only one or two
to know the revelations that lovely Circe
made to me alone. I'll tell you all,
so we can die with our eyes wide open now
or escape our fate and certain death together."
He proceeds to tell them about the Sirens, and they make it past this island. However, the men freeze, their ship "dead in the water," when they see the Clashing Rocks. Odysseus must realize that the same thing will happen if they know about Scylla, and so he makes
No mention of [her]—how to fight that nightmare?—
for fear the men would panic, desert their oars
and huddle down and stow themselves away.
Therefore, he withholds what he knows about Scylla, essentially condemning six of his men to die rather than risking that all should be lost. He puts on his armor, determined to fight her if he can, and "ashen terror gripped the men" as they watched Charybdis. It is at this moment that Scylla makes her move and snatches six men, gobbling them up quickly.
In other words, then, Odysseus, as a leader, must know how much information to tell and what information to withhold for the good of his crew. He wants to be honest with them, but he must also protect them as best he can. He has to be observant and discerning in order to make this decision; when he sees his men become paralyzed with fear at the Clashing Rocks, he must realize that he cannot tell them about Scylla or else the same thing will happen when they approach her. However, he is also very brave and just, staying above decks with his men rather than hiding down below and protecting himself; he also arms himself to fight off the monster if he can. These are all roles and responsibilities of a good leader, and Odysseus certainly does display these qualities in this chapter, making difficult decisions that could stump other people.