On colgaffneyis Website I recently received an inquiry about reenacting Scottish mercenaries of the 16th century. In response I wrote the following:
The first question: Highlander or Lowlander?
Lowlanders were very much part of the general Western European scene, and their soldiers would be similarly dressed and equipped. Scots had been using the long Swiss-style pike since the Flodden campaign early in the century. From 1572 on Scots were fighting with the Dutch against the Spanish, and so would be exposed to the most "modern" forms of warfare. You might be either pike or shot. Shot would either have the lighter arquebus or caliver, or the new heavy musket (with the forked musket rest). Oman's History of the Art of War in the Sixteenth Century is the classic book on European warfare of this era. Arnold's The Renaissance at War is more recent, and has lots of illustrations.
For irregular warfare look to the border reivers. Keith Durham's, The Border Reivers has pictures, but the outstanding work, and one of my all-time favorite history books, is George MacDonald Fraser's The Steel Bonnets. I don't know how many of them served as mercenaries overseas, but since their entire lives were about fighting for profit you might want to look at them.
Highlanders were culturally very much like their fellow Gaels in Ireland, and similarly dressed. Highlanders fought in Ireland throughout the middle and late 16th century, and were formidable opponents of the English. Ian Heath's The Irish Wars: 1485-1603 is a good place to start, with pictures. For more historical detail see Cyril Falls, Elizabeth's Irish Wars. I recently read Hill's Fire and Sword: Sorley Boy Macdonnell and the Rise of Clan Ian Mor, 1538-90, about the most famous Scot of these conflicts.
A Highlander near the end of this period might be wearing a belted plaid (great kilt). The first recorded description of this garment was in fact about Scottish Mercenaries in Ireland in 1594.
- Scottish Mercenaries of the 16th Century