In His explanation of Ezekiel's role as a prophet, God informs the man that he was to be a watchman for the people. Of what use is a watchman if the enemy's advance and all the pertinent details of his attack are already known? Anciently, a watchman would stand in a high place, upon a wall or a tower, and scan the horizon for enemies. When he saw them approaching, he was responsible for shouting a warning to the unsuspecting citizens that danger was near and that they needed to prepare for the onslaught. However, he did not know exact details—only what he could discern from his vantage point.
Once war begins, the most precious commodity is precise and timely information, and it is almost never transmitted in time to those who need it most. The best scenario a leader can ask for is to know as far in advance as possible that his enemy is on the march against him, for this gives him time to make the preparations necessary to secure his people and possessions, assemble his forces, and meet the enemy on the battlefield of his choosing. An excellent watchman just might give him the advance warning he needs.
However, this presupposes a physical attack. A continued reading of Ezekiel 33 clarifies that the prophet was not warning about a physical enemy but a spiritual one. Ezekiel's job was to warn the wicked in Israel to turn "from his way" (Ezekiel 33:8-11). His job as watchman was spiritual in nature! He was to warn against sinful lifestyles, against iniquity and wickedness, and to implore them to repent and live righteously. A companion passage in Ezekiel 3:16-21 makes this plain.
In other words, his role as prophet/watchman—just as a Christian minister's job is today—was heavily weighted toward preaching and teaching God's way of righteousness. It was essentially, like the gospel of the Kingdom of God, a warning message of repentance and an exhortation to growth in faith and obedience to holiness. In this regard, the prophetic hints about future events were, as they are to us, prods to motivate change before the coming, dreadful Day of the Lord.