In Book IV of "The Iliad," what does Agamemnon say to Diomedes? What feats does he bring up, and why?

Agamemnon rebukes Diomedes' because of Diomedes' shy nature and timidity in the face of battle: "...why are you so shy? So wary of the passages of war?" (lines 447-448, book IV, page 94 Fitzgreald translation). Agamemnon found him standing still with "combat cars and horses all around him" (line 442). He mentions the feats of Diomedes' father Tydeus: "he [Tydeus] would rather fight alone ahead of all his men" (lines 450-451), as a leader who charges forth, not one who lags behind, or waits for battle. Tydeus led a charge on the "ancient walls of Thebes" by carrying a message. He challenged those he encountered there to a wrestling match, and won. He also killed the fifty men who tried to ambush him on his return to his fellow soldiers. These feats showed great courage, wheras Diomedes showed cowardice. The final blow from Agamemnon, and a summation of the point can be found in the line, "Weaker than he [Tydeus] in war, the man he fathered [Diomedes]" (line 482). Agamemnon's entire rebuke can be read from lines 440-483.