Mennonite Brethren are part of the larger Mennonite or Anabaptist movement, and, as such, (at least theoretically) share a common Biblical theology. This Anabaptist or Mennonite theology centers on the theme of serious discipleship. The church is made up of those who trust in Jesus Christ, and is called to take seriously his commands. The Sermon on the Mount is seen as normative for believers, rather than relegated to some future age. Believers are called to follow the "way of the cross", of suffering for the sake of obedience to Christ. Christian service is quite important, thus such agencies as Mennonite Central Committee and Mennonite Disaster Service have been formed to serve wherever there are needs. The emphasis on meeting physical needs also arose historically because of the persecution of Anabaptists, and the frequent need to leave one country or another and start over with nothing. Because Jesus said to "love your enemies", Anabaptists are pacifists. There is a heavy emphasis on the guidance of the Holy Spirit through the church, thus historically a strong reliance on consensus in decision-making.

Several movements prior to the beginnings of the Mennonites in the 1500s developed some of the themes that were taken up by the Mennonites. One such movement was the Waldensians, beginning around the year 1170. Peter Waldo, a wealthy merchant, underwent a deeply felt religious experience. He gave away his possessions and founded this movement. Major emphases included the Bible in the common tongue as the rule for life and faith; a strong missionary and evangelism emphasis, with every believer entitled to minister; a special emphasis on the Sermon on the Mount; and an emphasis on being possessed by the Holy Spirit. They were soon persecuted.

The Bohemian Brethren, later called the Moravian Brethren or the Unity of the Brethren (Unitas Fratrum), arose in Prague in 1453. They were influenced by the Waldensians, by the followers of John Huss, and by the followers of John Wyclif (called Lollards.) They too emphasized the Bible as the sole source of teaching, and a holy life as the "indispensable proof of saving faith." They regarded the Sermon on the Mount as normative, including pacifism. The term Brethren in the name emphasized the priesthood of all believers.

A third influence came from Bernard of Clairvaux, a 12th Century mystic. He emphasized a living relationship with God rather than formality.

These helped prepare Europe for the Reformation in the early 1500s. An incident often looked to as the start of the Reformation is Martin Luther's posting of 95 Theses, or points he wanted to debate with the authorities, on the door of the Wittenberg (Germany) church in 1517. Three major groups (besides the Roman Catholics) arose from this Reformation - Lutherans, Calvinist or Reformed, and Anabaptist. All three groups emphasized individual salvation by faith, and the authority of Scripture. The Anabaptists differed primarily from the other groups in two additional emphases: their view of the church, and an emphasis on discipleship. They viewed the church as a voluntary association (rather than the state church of the other three groups), pure in that it was made up only of those who were saved (Believer's Baptism made one a member), and separated from the world and therefore often persecuted. Because they took the Sermon on the Mount seriously, they put a strong emphasis on discipleship (living the way Jesus taught) and ethics, including a nonviolent stance.

Anabaptist means "again baptizers", a name used by others because of the emphasis on Believer's Baptism. The Roman Catholics, Lutherans, and Calvinists all practiced infant baptism, thus referred to Believer's Baptism as a re-baptism, which they felt was wrong. The Anabaptists viewed baptism as a step of faith taken as a public witness of salvation, and of joining the visible church.

An early Anabaptist document is the Schleitheim Confession of 1527. It covered 7 articles of faith: (1) Believer's Baptism; (2) a procedure for excommunication along the lines of Matthew 18 (This was part of the emphasis on a pure, separated church); (3) the Lord's Supper, seen as a memorial feast for believers only; (4) separation from evil, especially drinking and the use of force; (5) a pastor's qualifications; (6) separation of church and state (the sword "ordained of God outside the perfection of Christ", and thus Christians were not to participate in government); and (7) oaths were forbidden.

In 1534, at Muenster, a group set up the "kingdom of God on earth" under the leadership of Jan of Leyden. They were heavily immoral, forcing group marriage on the people, and quite violent, and were eventually annihilated by the authorities. Because they practiced adult baptism, they were held up as an example of Anabaptist fanaticism, although their theology centered more on Post-Millennialism than on the historical emphases of today's Anabaptists or Mennonites. Calvin wrote a book entitled "Against the Anabaptists" about this incident, and Communist philosophers have pointed to this as a forerunner of Communism. Educated Calvinists use this still today to speak against "Anabaptists", a point to consider before changing the denominational name from "Mennonite Brethren" to "Evangelical Anabaptists", as has been proposed.

In 1536, Menno Simons, who had been a well-educated priest familiar with Luther's writings and with the New Testament, became the leader of the Anabaptist movement, becoming pastor of a group of Waldensians. He had been intellectually convinced of Anabaptist theology long before undergoing a "heart change". His own brother had been among the heretics annihilated at Muenster. The term "Mennonite" comes from his name. He urged leaders to "seek the Lord and rule justly", and thus apparently felt believers could participate in government.

Due to persecutions, there were constant migrations. Mennonites also developed good skills in business and agriculture.

In the late 1700s, there were large numbers of Mennonites in Prussia. The government was becoming increasingly militaristic. At this time, Catherine II (Catherine the Great) of Russia invited them to move to Russia. Many of the poorer Mennonites migrated at this time. Few ministers moved, as they were generally selected from among the affluent and had more to lose.

The Mennonites formed their own separate German-speaking communities in Russia, and took on roles of both church and state. By 1812, many were "Mennonites" not because of belief in Christ, but because their parents were. A movement known as the "Kleine Gemeinde" or "Little Congregation (or Community)", in contrast to the "Grosse Gemeinde" or "Large Community", arose. They expressed alarm at the "worldliness" among Mennonites there, as shown by smoking, drinking, use of force, card playing, and musical instruments. In contrast, they emphasized simple living. They rejected higher education, and were amillennial in eschatology. At the time, they had little influence due to their extreme narrowness. They developed into the Evangelical Mennonite Conference and the Krimmer (Crimean) Mennonite Brethren.

Worldliness continued. The General Conference Mennonites describe the Mennonites of the 1840's as "lethargic." Church discipline was lax, and another reform movement arose, with influence from German Baptists and Lutheran Pietists, as well as the historic Anabaptist theology. At this point only elders could hold Communion or baptize, while anything else in the area of ministry was open to other leaders. There would be only one elder for a large region (several communities.) This reform movement asked for a separate Communion service to be held, excluding those not living the Christian life. This request was refused by the leaders, so the group went ahead and held their own separate Communion in December 1859. The next month they organized as the Mennonite Brethren. The remaining Mennonites did not remain worldly - revival came to them also later.

A smaller group arose within the Mennonite Brethren, known as the "Froehlicker Richtung", or "Joyful Brethren". They referred to any not of their movement as the "Babylonian Church", and called fellowship with such others, even if Christians, "smearing", and to be avoided. They emphasized shouting, joyful singing with tambourines, and dancing in worship, criticizing those who didn't do so as "Pharisees", "sinners", "not free", "in the flesh and carnal". They described themselves as "liberated", "strong ones", and taught a "doctrine of freedom" that allowed immoral behavior. They regarded it as "fellowship with the world" to even greet your own close relatives if they were unbelievers. The "doctrine of freedom" was formally condemned in 1862 by the Mennonite Brethren, and other "Joyful Brethren" excesses were condemned in 1865, including the outlawing of tambourines.

In 1910, P.M. Friesen described many of the MB founders as being incompetent. He stated some were brought to repentance, others were "expelled by the wholesome element", and others left of their own accord.

Changes were also taking place in Russia. In 1861 serfdom was abolished, and as a result in 1870 Russia instituted universal military service, with a ten year moratorium before it was to take effect among the Mennonites. As a result many Mennonites migrated again. In 1874 this involved many Mennonite Brethren who moved to the central United States (Kansas and the Dakotas), where the climate and agriculture were similar. Another major wave of emigration came during and after the Russian Revolution of 1917. Mennonite Central Committee was formed at this time for famine relief.

Other movements also influenced the Mennonite Brethren in the United States, among them Dispensationalism and Fundamentalism. In 1960, the Mennonite Brethren and the Krimmer Mennonite Brethren merged to form today's Mennonite Brethren. One interesting difference was the largely amillennial eschatology of the Krimmer MBs and the largely premillennial eschatology of the MBs. The current MB Confession of Faith is neither amillennial nor premillennial, but emphasizes that the Lord will return.

Some of the issues recognized by the MBs today include dealing with increased/increasing affluence and education, the role of charismatic gifts and enthusiasm in worship, the propriety of women in ministry, ethnic perceptions of Mennonites in general, and a struggle with pacifism as a Biblical doctrine.