--Patzinak
[…] The execution of the plan [to attack Greece] required Bulgaria to become an Axis ally or at least to agree to a movement of troops across her territory. Bulgaria showed considerable reluctance to accede to German demands, but in the end she was compelled to yield. In January and February 1941 military negotiators took up the matter of German-Bulgarian combined operations. Agreement was complicated by the fact that consideration had to be given to the danger of Bulgaria's being attacked by Turkey or Greece between the period Germany began to move her troops and the time Germany was ready to launch the attack against Greece.
Although Hungary, Rumania, and Slovakia had joined the Tripartite Pact at the end of November 1940, Bulgaria postponed taking this step until 1 March 1941. By that time German forces were moving through Bulgaria for the attack on Greece. […]
Bulgaria had agreed to the passage of German troops for the attack against Greece and, after the coup d'etat in Belgrade, also against Yugoslavia, but she took no active part in these campaigns. […] [Also,] Bulgaria took no part in the war against Soviet Russia. […]
[Beginning in] the summer of 1940 Bulgaria […] received large quantities of ammunition, marine mines, and some coast artillery guns. Since Bulgaria took no active part in the war against the Soviet Union, her 1941 requests for war equipment were only partially met. She received a few tanks, armored reconnaissance cars, motor vehicles, and signal equipment. In 1942 Bulgaria began to receive increasingly large shipments, including 180 Belgian light field howitzers with ammunition, 80 French heavy field howitzers with ammunition, several 220-mm howitzers with ammunition, and other materiel. In 1943 the Bulgarian army requested the complete equipment needed for ten infantry divisions, but only some German materiel was sent in compliance with this request. […]
Late in 1940 […] a colonel from the German Army General Staff was sent to the Bulgarian High Command to establish liaison. Further negotiations were conducted by officers of the Bulgarian High Command at German headquarters, and when a German army began to assemble in southern Rumania, its commanding general was assigned the duty of continuing negotiations on behalf of the German Army High Command. [After Greece] liaison with the Bulgarian High Command was again left to the military attache who organized the German training staff to assist the Bulgarian army. [Due to increasing] German assistance in the organization and training of the Bulgarian army [and the possibility of war spreading to Bulgaria], it also became necessary to establish an office of the German General with the Bulgarian Armed Forces High Command. The military attache became its Chief of Staff, and a colonel was assigned as deputy military attache. […]
[The] small advisory staff initially assigned [to Bulgaria] in summer 1942 [eventually grew to a battalion-size…] all service arms […] combat training school, [with whose aid] the Bulgarian army, then ten divisions strong, was greatly improved. Up to 400 company and platoon leaders could be assigned simultaneously to this school for a complete course of training. Special courses were given to older officers, up to and including generals. The results of his training were good, because the top levels of the Bulgarian army encouraged the program. The German instructor personnel was carefully chosen, and the instruction was given to all ranks of the army. In view of the short training period, however, the results could only be considered a beginning. […]
Apart from minor actions against partisans, the Bulgarian army did not fight alongside German troops, so that military collaboration between the two countries was never put to a real test. What collaboration there was in anticipation of combined action was carried out with relatively little friction. There were two occasions when preparations were made to move German troops into Bulgaria, one in March 1941, and the other in 1943 when it appeared possible that Bulgaria and Germany might join forces to fight Turkey. German training activity in Bulgaria, however, was particularly successful. This may well have been largely due to the fact that the Bulgarian army was not actually in the war. Moreover, the strength and quality of the German training teams were adequate for the task, and the Bulgarian army required all its troops, including generals, to receive German training. Germany's high reputation in Bulgaria and Bulgaria's readiness to accept German military principles were further favorable factors. […]