Jesus said  "Go you into all the world and preach the Gospel!"  Mark 16:15. and Paul describes it as "The Gospel of Peace that brings good tidings."  Romans 10:15.

When Chamberlain came back from Munich waving his famous piece of paper I as intrigued when I saw the bill hoardings for I knew that they were straight from the Bible. "Blessed are the Peacemakers"

We must recognise and honour all men of goodwill who have striven over the years to secure international peace even though some of them, like Chamberlain, have failed.  Men like Kissinger who negotiated peace between the Arabs and Israelis in 1973, who brought about the end of the war in Vietnam in 1975, and was awarded a well deserved Nobel Peace Prize.  Kissinger went on record as saying that he prayed every morning!

But Jesus was not really talking about international peace, but about something much more fundamental and individual, the blessing of the song proclaimed by the angels "Peace on earth and mercy mild, God and sinner reconciled!"

But it was only after three years of intensive training at the feet of the greatest Teacher the world has ever known that the disciples received their commissions to go into all the world and preach this gospel of peace and reconciliation to every creature!

It might prove useful to reconstruct their training programme from what evidence is available to us.
 

YEAR ONE.
Jesus began by gathering His disciples together.  The first disciple who is named is Andrew.  "And one of the two who heard John the Baptist speak and followed Him was Andrew.  And he first finds his own brother Simon and says to him `We have found the Messiah!'  And he brought him to Jesus."  John 1:40.   Then later we read  "Jesus walking by the Sea of Galilee saw two brothers, Simon called Peter, casting a net into the sea, for they were fishermen.  And He says to them  `Follow me, and I will make you fishers of men!'"  Matthew 14: 18-19.   Later still we read  "He saw two other brothers, James and John, and immediately they followed Him.  Matthew  14:21.  Then one by one he adds to His band of followers which seems to have grown to a fairly large crowd of around eighty.
 

YEAR TWO
After a night of prayer Jesus calls his large band of followers to chose His inner band.  "And when it was day he called unto Him His disciples whom He also named apostles.  Simon (whom He also named Peter), and Andrew his brother, James and John, Philip and Bartholomew, Matthew and Thomas, James the son of Alphaeus, and Simon called Zelotes, and Judas the brother of James, and Judas Iscariot which was also the traitor."  Luke 6: 13-16.
 

At the end of the year Jesus sends them out on a trial run for field training.  "Then He called His disciples together and gave them power and authority...and sent them to preach the Kingdom of God."  Luke 9: 1-2.
The actual preaching tour began after the second rejection of Jesus at Nazareth.  "And He marvelled at their unbelief and He called unto Himself the twelve and began to send them forth two by two."  Mark 6: 5-6.
It is not easy to work out the length of this preaching tour, but it was certainly much more than a long weekend!  At the beginning of Matthew Chapter 10 Jesus sends out His disciples, giving them full instructions.  Chapter 11 sees their departure.  "And it came to pass when Jesus had made an end to commanding His twelve disciples He departed thence to teach, and when John heard in prison the works of Christ he sent two of his disciples."  Matthew 11: 1-2.
This mission of the twelve certainly created a great stir for we read in Luke 9:7 that "Herod was perplexed" by it all.

YEAR THREE.
Though it is difficult to say how long the preaching tour lasted, it must have been at a minimum three or four months during which they travelled many miles and preached in many places.  Certainly much happened while they were away.
When they returned they reported to Jesus.  "Then the apostles gathered to Jesus and told Him all things, both what they had done and what they had taught."  Mark 6:30
By this time John the Baptist was dead and buried.  "And his disciples  (John's disciples)  came and took up the body and buried it, and went and told Jesus."  Matthew 14:12
There was however small chance of peace and rest for when the people saw Jesus with His disciples they recognised them and followed them and two verses later is the story of the feeding of the multitude.  "And Jesus went forth and saw the great multitude and was moved with compassion and healed their sick.  Matthew 14:14.  The feeding of the 5,000 followed immediately.
It is a surprising thought that part of the training of the twelve should be that they were actually away from Jesus for such a long time!  Perhaps this was their preparation for the not too distant day when they would be on their own!
At the very end of His ministry after three years when the training programme was fully complete Jesus as the Risen Christ commissioned the disciples to go as Peacemakers reconciling men with God on a permanent basis!
 

Or, to put it as it affects us, it is only when we have been schooled by God an passed through His grades that we are ready in His sight to preach to others!  There is a difference between testimony and teaching.  A new convert can testify, but anyone who wants to preach must first grow in the grace and knowledge of the Lord Jesus just as the disciples did before Jesus felt they were ready to be sent out!  Even in spiritual things we must learn to walk before we can run!

In passing, some people experience needless difficulty with Matthew 20:16 which says "Many be called but few chosen", saying that this refers to the ordination of the twelve since only twelve were chosen.  Then they proceed to work out a doctrine of election which suggests that God chooses some and rejects others.
 
 

But if we follow what happened to those who were not chosen as apostles we find that six months later Jesus "appointed another seventy" who were sent out in addition to and in the same manner as the twelve.

The simple reason why FEW are chosen is that FEW respond to God's call in the first place, and, even for God, His choice is restricted by this reality!

The owner of a cotton plantation was bantering with one of his Christian slaves about the doctrine of election.

"Do you think, then, that I am elected, Ratus?" he asked.

"Well!" the slave replied "I'se never heard of an election without a candidate!"

The Bible lists at least four things that God cannot or will not do
God cannot LIE.  "It was impossible for God to lie."  Hebrews 6:18.
God cannot CHANGE.  "For I am the Lord;  I change not!"  Malachi 3:6.
God cannot be TEMPTED.  "God cannot be tempted with evil!"  James 1:13.
God cannot FAIL.  "I will not fail you nor forsake you!" Joshua 1:5.

Perhaps forcing His choice upon the unresponding is another!  But certainly all who do respond to the call of God are chosen for something!  And those who follow His leadings will ultimately be the bearers of His gospel of peace, the reconciliation of individual men with Him, and, as such, will be called "the children of God"