When the Spanish Civil War started in 1936, Spain had few tanks and little experience with them. A dozen Renault FTs, a handful of Schneider CAs, and four Trubia A4s (a domestic derivative of the FT) constituted the entire tank force of Spain. Of those tanks, the Republicans would start the war with 5 FTs, 4 CAs, and 1 A4, while the Nationalists had 5 FTs and 3 A4s. The only domestic production during the war would be a dozen Trubia Naval tanks. Both versions of the Trubia tank were armed solely with machine guns.
The vast majority of the tanks in the war came from three nations that ignored the arms embargo on both sides - the Soviet Union, Germany, and Italy. The Soviet Union would supply 281 T-26 tanks and 50 BT-5 fast tanks to the Republicans, while the two fascist nations would provide 122 Panzer I tanks and 155 L3/33 and L3/35 tankettes.
Per Stephen Zaloga's research, the deliveries of Soviet tanks were as follows:
12 Oct 1936 - 50 T-26
25 Nov 1936 - 37 T-26
30 Nov 1936 - 19 T-26
06 Mar 1937 - 60 T-26
08 Mar 1937 - 40 T-26
07 May 1937 - 50 T-26
10 Aug 1937 - 50 BT-5
13 Mar 1938 - 25 T-26
Meanwhile, the Nationalists received the following deliveries:
August 1936 - 5 L3
October 1936 - 41 PzKpfw I, 10 L3
December 1936 - 21 PzKpfw I, 20 L3
Jan/Feb 1937 - 24 L3
March 1937 - 24 L3
April 1937 - 12 L3
August 1937 - 30 PzKpfw I
September 1937 - 16 L3
December 1937 - 10 PzKpfw I
April 1938 - 12 L3
Nov/Dec 1938 - 32 L3
January 1939 - 30 PzKpfw I
These would be the primary armored fighting vehicles of the Spanish Civil War.