By definition, a Mennonite is a member of a Protestant church rising out of the Anabaptists, a radical reform movement of the 16th Century Reformation, and named for Menno Simons, a Dutch priest who consolidated and institutionalized the work initiated by the moderate Anabaptist leaders.
Backing up for a moment, one needs to define Anabaptist. An Anabaptist is one who rejects infant baptism, believes in separation of church and state, nonswearing of oaths, and nonresistance. (Here is a little aside. Frequently the terms pacifist and conscientious objector are confused or even used interchangeably. A conscientious objector is one who by reason of one's conscience is against killing another person, thus believing that war is wrong. A pacifist is simply one who loves peace. A soldier can be a pacifist - he/she loves peace but will fight to protect that peace. A Mennonite is a conscientious objector.)
The Anabaptist movement began in Zurich, Switzerland on January 21, 1525. The three men responsible for the beginning of this movement were Felix Manz, George Blaurock and Conrad Grebel, the latter being the acknowledged leader. This was the beginning of the Swiss Brethren, a group that formed in the face of imminent persecution for their nonconformity to the demands of the state church led by the Reformed theologian Huldrych Zwingli. The Anabaptist movement involved the issue of infant baptism, which the Ananbaptists felt was wrong based on Biblical studies, but more importantly, the real issue was the nature of the church. Christ, according to their view, is Lord of the Church and only those who submit to that Lordship can be true members of His body. Furthermore, the body of Christ receives its guidance from Christ himself through the Scriptures and the Holy Spirit, not from or through the civil magistracy.
The Anabaptist movement spread northward through Germany and into the Netherlands, where in 1536 Menno Simons, a former Catholic priest, joined the Anabaptist movement and became its acknowledged spokesman. Persecution had a great deal to do with the spreading of the movement.
Some other Anabaptist movements included one in central Germany under the leadership of Hans Hut, Hans Denk and Pilgram Marpeck. Another movement came to be known as the Hutterian Brethren because of the coordinating leadership of Jakob Hutter, and this group was known for their communal living and for an intense missionary zeal that continued into the 17th century.
Persecution drove many Mennonites from Switzerland in the 18th century into Germany, Alsace, The Netherlands and the United States. Before this time a major schism occurred when the Swiss Mennonite bishop left the Mennonites to form the Amish Church in an attempt to preserve Biblical discipline among the membership. Many people erroneously believe that the Mennonites split off from the Amish, but the reverse is the case.
Beginning in 1663, Mennonites emigrated to North America to preserve the faith of their fathers, to seek economic opportunity and adventure, and especially to escape European militarism. They retained their German language, partly as a religious symbol and partly as insulation against their environment. Their main concern was to be left alone to worship God according to their conscience and tradition.
Mennonites believe in the doctrine of the Trinity, that God is three Persons, - Father, Son and Holy Spirit. They affirm the Scriptures in their entirety, both the Old and the New Testaments, believing that both Books are the inspired Word of God. They stress the importance of baptism upon confession of faith. Defined, this means that everyone is a sinner, saved by believing in the Lord Jesus Christ as their Personal Saviour, who died on the Cross, was resurrected on the third day, and then ascended into Heaven where He is seated on the right hand of God, having sent His Holy Spirit to indwell them and be their Guide on Earth. This is the core of their theology. Mennonites may also advocate a number of church practices, such as the ceremony of feet washing, plain clothes, and ordination of ministers by lot. In addition, they believe in nonconformity to the world, nonswearing of oaths, and nonresistance in lieu of military service.
Mennonite worship services are sermon-centered with a very simple service. Until fairly recently in the United States, particularly in Lancaster County, PA, most did not have organs or pianos in their churches and are still known for their acappella singing. Their churches were also very simple in design, with no steeples, usually made of brick with blinds at the windows instead of curtains. (Depending upon the degree of conservatism, many still are like this.) Mennonite ministers are self sustaining and not paid by their congregations in many areas of Pennsylvania. In addition to their preaching responsibilities, they also hold down another job to support themselves and their families.
There are varying degrees of Mennonitism, ranging from the very conservative to the least conservative. These varying groups are way too numerous to even mention here. Most Mennonite congregations are joined together into numerous conferences, seven of which are in North America.
Mennonites are also well known for their social concerns. An emergency relief committee for national and international aid was formed by the Dutch Mennonites in 1725, and is still active. In 1920, North American Mennonites formed the Mennonite Central Committee for the same purpose, initially to relieve famine in Russia. This Committee continues to this day.