The leaders of the land should have been preparing to protect their people instead of partying. Proper preparation for war included oiling the shields. Shields made of leather were oiled to prevent them from drying out, which would cause them to tear or burst. The smooth leather was also said to help deflect the enemy's blows.
5 They prepare the table, they spread the rugs, they eat, they drink. Arise, O princes; oil the shield!