1939 - The Battalion is mobilised
At in September, the 17th Infantry Brigade gathers, formed of the 2nd Seaforth Highlanders, the 2nd Northamptonshire Regiment and the 2nd Royal Scots Fusiliers.
Each battalion's strength was increased by officers and men arriving from the training depots and on being recalled to the colours.
The brigade forms an Anti Tank company and each of the battalion's donates an officer and a platoon's worth of troops to man it.
On the 13th of October the battalion (minus D Coy) embarks on the SS Brighton from Portsmouth.
D company follows a day later.
In , where the brigade landed at on , the 2nd Seaforth were replaced by the 6th Seaforth from the 51st () Division.
Thereafter the 17th Brigade remained unchanged throughout the war.
The original brigade commander was Brigadier M. G. N. Stopford.
The 5th Division, consisting of the 13th, 15th, and 17th Brigades, came into being in France late in 1939.