The Dorset Trained Bands were a part-time militia force recruited from Dorsetshire in South West England, first organised in 1558.

They were periodically embodied for home defence and internal security, including the Spanish Armada campaign in 1588, and saw active service during the Wars of the Three Kingdoms.

In 1584 Dorset was charged with finding 800 'shot' (armed with firearms such as calivers and muskets), 200 bowmen and 500 'corslets' (body armour, signifying pikemen).

[13][14][15] In November 1587 Dorset's full strength was estimated at 3,220 'able men furnished, besides pioneers, carters and victuallers and such others as are appointed to keep home for guarding the sconces, bulwarks and bridges'.

Early in 1588 the veteran Sir John Norreys was sent with his officers to supervise the preparations in the maritime counties of Dorset, Hampshire, Sussex and Kent.

A force of 120 lancers, 40 light horse, and 600 pioneers were assigned to the main army, to be accompanied by a suggested 2000 foot under deputy lieutenant George Trenchard.

[1][16][17] The arrival of the Spanish Armada that summer led to the mobilisation of the trained bands on 23 July, the Dorset cavalry and 1000 foot being sent to London.

The rest of the Dorset men went to their stations when the fire beacons were lighted and shadowed the Spanish fleet as it sailed up the English Channel.

Conduct money was recovered from the government, but replacing the weapons issued to the levies from the militia armouries was a heavy cost on the counties.

The JPs of Dorset were heavily criticised for their choice of two completely unqualified men to act as captains[1][20] With the passing of the threat of invasion, the trained bands declined in the early 17th Century.

On the march north Lieutenant William Mohun attempted to impose discipline on the men of Captain Lewkner's Dorset company.

In retaliation the soldiers stormed the officers' quarters, allowing Lewkner and the Ensign to escape, but beating Mohun with cudgels and leaving him for dead.

Mohun recovered consciousness and was receiving medical attention when the soldiers heard of his recovery, broke into the house and finished him off after a fight.

[1][25][26][27][28] Early in the conflict in September 1642 Dorset Trained Bandsmen were called out by both sides for the Siege of Sherborne Castle: Hugh Rogers of Bryanston assembled around 1000 TB foot for the Marquess of Hertford's Royalist army, and joined the garrison, while Sir Thomas Trenchard organised another regiment for Parliament, which formed part of the besieging force under the Earl of Bedford, which arrived on 2 September.

[1][39][40][41][42] The militia were frequently called out during the reign of King Charles II; their duties included suppressing non-conformist religious assemblies (of which there were many in the West Country) under the Conventicle Act 1664.