Like the wooden horse given to the city of Troy, the Cross of Jesus Christ is not at all what it seems. It is dead wood that produced the ripened fruit of eternal life; it's a sword disguised as gallows. 

At Vespers for the Exaltation of the Holy Cross, we hear these words:

Come, all ye nations, let us worship the blessed Tree whereby everlasting righteousness hath come to be; for he who by the tree deceived our forefather Adam, is himself deceived by the Cross, and he who by tyranny held fast the royal house, falleth, cast down by a strange fall. By the blood of God the venom of the serpent is washed away, and the curse of the just condemnation was lifted by the Righteous One when He was condemned by an unjust sentence; for it was fitting that the tree be healed by a Tree, and that, by the sufferings of the Dispassionate One on the Tree, the sufferings of the condemned be loosed.” 

By this Sign Conquer

In the year 306, Constantine was declared Augustus (emperor) by his army in York, England.  Later, on 28 October in the year of our Lord 312, Constantine and his men fought Maxentius in the battle of the Milvian Bridge on the Tiber River not far from Rome.

Before the battle, Constantine saw a cross in the sky accompanied by Greek words saying "In this sign Conquer.” Constantine had the cross reproduced on the standards and shields of his soldiers, he won the battle, entered Rome victorious, and the Imperium Christianum “the Christian Empire,” was born.

In the Akathist Hymn to Saints Constantine and Helen, Kontakion II we hear:

Beholding Maxentios and Maximian trampling upon the pasture of Christ, you took boldness in God, O Constantine, and having arrayed yourself in the weapon of the Cross, and having overcome tyrants, you cried out to the Lord: Alleluia.

Yes, the cross is a weapon, and not just A weapon, it’s THE weapon. It’s the weapon Christ wielded when He ascended it above Golgotha, planting both the Tree of Life to feed the ever-living, and piercing the ground into Hades, which held captive the dead since the days of Adam.

At Great Vespers on the eve of The Exaltation of the Cross, we hear:

Elevat, today, the Tree of life, which was planted in the place of the skull, whereon the preeternal King wrought salvation in the midst of the earth, sanctifieth the ends of the earth; and the temple of the Resurrection is renewed…

And at Great Vespers on the 3rd Sunday of Lent, we hear:

Hail! life-giving Cross, the fair Paradise of the Church, Tree of incorruption that brings us the enjoyment of eternal glory: through thee the hosts of demons have been driven back; and the hierarchies of angels rejoice with one accord, as the congregations of the faithful keep the feast. Thou art an invincible weapon, an unbroken stronghold; thou art the victory of kings and the glory of priests. Grant us now to draw near to the Passion of Christ and to His Resurrection. Hail! life-giving Cross, unconquerable trophy of the true faith, door to Paradise, succor of the faithful, rampart set about the Church. Through thee the curse is utterly destroyed, the power of death is swallowed up, and we are raised from earth to heaven: invincible weapon, adversary of demons, glory of martyrs, true ornament of holy monks, haven of salvation bestowing on the world great mercy.”

The Cross, The Preserver of the Universe

In 1947, St. John Maximovich gave a sermon on the feast of the Exaltation of The Cross in Shanghai. Here is a portion of that sermon: 

“In the Prophet Ezekiel (9:6) it is said that when the Angel of the Lord was sent to punish and destroy the sinning people, it was told him not to strike those on whom the "mark" had been made. In the original text this mark is called "tav," the Hebrew letter corresponding to the letter "T," which is how in ancient times the cross was made, which then was an instrument of punishment…

Having stretched out His hands upon the Cross, the Saviour with them as it were embraced the world, and by His blood shed on it, like a king with red ink, He signed the forgiveness of the human race.

Through the Cross, He descended with His soul into hell so as to raise up from it the souls who were awaiting Him. By the Cross, Christ opened the doors of paradise which had been closed after our first ancestors had been banished from it. The Cross was sanctified by the Body of Christ which was nailed to it when He gave Himself over to torments and death for the salvation of the world, and it itself was then filled with life-giving power. By the Cross on Golgotha, the prince of this world was cast out (John 12:31) and an end was put to his authority. The weapon by which he was crushed became the sign of Christ's victory.

The demonic hosts tremble when they see the Cross, for by the Cross the kingdom of hell was destroyed. They do not dare to draw near to anyone who is guarded by the Cross.

The Cross is the unconquerable weapon of pious kings in the battle with enemies. Through the apparition of the Cross in the sky the dominion of Emperor Constantine was confirmed and an end was put to the persecution against the Church. The apparition of the Cross in the sky in Jerusalem in the days of Constantius the Arian proclaimed the victory of Orthodoxy…

The "sign of the Son of Man" (Matt. 24:30), that is, the Cross, will appear in the sky in order to proclaim the end of the present world and the coming of the eternal Kingdom of the Son of God….The Cross then will save from eternal perdition all who conquered temptations by the Cross, who crucified their flesh with its passions and lusts, and took up their cross and followed after Christ.

But those who hated the Cross of the Lord and did not engrave the Cross in their soul will perish forever. For "the Cross is the preserver of the whole universe, the Cross is the beauty of the Church, the Cross is the might of kings, the Cross is the confirmation of the faithful, the Cross is the glory of angels and the scourge of demons" (Octoechos: Exapostilarion, Monday Matins).”

And St. Ephrem the Syrian (Hymn on Virginity XVI, 10) says:

Greatly saddened was the Tree of Life when it beheld Adam stolen away from it;
it sank down into the virgin ground and was hidden—to burst forth and reappear on Golgotha;
humanity, like birds that are chased,
took refuge in it
so that it might return them to their proper home.
The chaser was chased away,
while the doves that had been chased now hop with joy in Paradise.

The Cross is a Weapon

The cross is a weapon; so much so that the mere trace of it by the hand can rip the Red Sea in half and put it back together again. The weapon of the cross tore apart the veil of the temple because it tore apart the partition between the seen and the unseen. 

In his Paschal Sermon, St. John Chrysostom describes it this way:

By descending into Hell, He made Hell captive. He embittered it when it tasted of His flesh. And Isaiah, foretelling this, did cry: Hell, said he, was embittered, when it encountered Thee in the lower regions. It was embittered, for it was abolished. It was embittered, for it was mocked. It was embittered, for it was slain. It was embittered, for it was overthrown. It was embittered, for it was fettered in chains. It took a body, and met God face to face. It took earth, and encountered Heaven. It took that which was seen, and fell upon the unseen.”

I'll leave you with the Kontakia of  St. Romanos On the Adoration of the Cross: 

When the first creature was shut out from Paradise, An order was given to the Cherubim to guard the road; But take My cross On your shoulders, and thus go into Eden with haste. If the sword of the Cherubim did not see you wearing the title rights of the inscription, The sword of flame which stands guard would consume you But, taking the inscription of My cross, robber, Walk up to the Cherubim, And they will know the symbol of life and they will give into your hands The power to open and to lead My friends Into Paradise.”