In Isaiah 2:4, where the prophet writes we shall study war no more, he is not taking about the wars of mankind, such as the Second World War of the Iraq War. In a fallen world, wars will not cease. The Word of God is addressed to believers. The prophet is talking about the wars that the apostle Paul describes in the New Testament, the war "against principalities, powers and rulers of darkness in this world." That is a war Christians must fight every day. When we study the scriptures we are, in effect, studying war.
But in time we shall lay down our swords and shields. Sword in this case is the Word of God. We won't stop believing or standing on the Word of God. But we won't need it as a sword. We won't be attacking anyone. And we shall lay down our shield of faith. We will always have faith. Faith in God's Word and we wil use faith, but we won't need it as a shield. Nothing will be attacking us.
On that day of peace, we shall study war no more.
(Just in case you wanted to know)