Romania’s accession into the Entente (27 August 1916) opened a second front on the Balkans; however, already since October of 1915, Russian warships subjected Bulgaria’s northeast coast to devastating shelling. On 1 September 1916, Bulgaria declared war on Romania, and Third Army, led by Lt. General Stefan Toshev, advanced into Dobrudzha (2 September), where it faced Romanian, Russian, and Serbian forces. The offensive’s initial objective was the capture of the Tutrakan Fortress. The charge was launched on 5 September. By the evening of the following day, enemy’s resistance was completely crashed and the Romanian commandant of the fortress, Gen. Constantin Teodorescu, sent to the commander of 4th Infantry Preslav Division, Maj. Genаral Panteley Kiselov, a letter of capitulation. To secure the right flank of the advancing troops, 1st Cavalry Division battled Russian and Romanian units at Kochmar, Dobrich, Kurtbunar (today, Tervel), and Karapelit. On 4 September, the troops of the Varna Fortified Point, under the command of Maj. General Todor Kantardzhiev, entered Dobrich. The following day, the many times superior combined Entente force launched an operation for the re-capture of the town. The unavoidable loss of the just-freed Dobrich was prevented through the intervention of the staged west of the theatre Cavalry Division, led by Maj. General Ivan Kolev, with the two attached battalions of 16th Infantry Lovech Regiment.
After 11 September, Third Army switched to a general offensive in Northern Dobrudzha. Enhanced with German, Turkish, and Bulgarian divisions, in three-day grizzly engagements it apprehended the Cobadin position (21 October), upon which it took Constanţa, Medgidia, Cernavoda, Hârşova. The successful operations of the allies in Transylvania, and of Third Army in Dobrudzha, provided the setup for an offence in the Wallachian Plane – the newly formed Danube Army forced the Danube and captured Bucharest (6 December), while Third Army assumed controlled over all of Northern Dobrudzha and took positions along the lower courses of the rivers Seret and Danube.
His Royal Majesty’s Navy, under the command of Col. Konstantin Kirkov, directly and indirectly supported the actions of Third Army from the Black Sea coast and countered the enemy naval forces. Its objectives included also capturing the Dobrudzha’s coast, mining the approaches to the enemy ports and minesweeping, carrying out aerial assaults on the enemy bases, convoying the transports between Varna and the newly-freed ports. All Navy resources were mobilized.
In early September of 1916, while the battles for Dobrich were fought on land, the first Bulgarian landing was carried out. It was executed with five torpedo boats under the detachment commander Lt. Captain Rashko Serafimov, which transported the units of the newly-formed Port Battalion. The landing employed the tactic of the surprise attack, with advance aerial reconnaissance preparation. Thus, regardless of the enemy’s numeric superiority, the military action was crowned with success. Balchik, the port of Kavarna, the lighthouse and the post at Cape Kaliakra were captured, and the Romanian units retreated north. From 7th to 18th of October, First Port Company led by Lieutenant Nikola Naumov was attached to 1st Cavalry Division. It received its baptism by fire in the gory battles at Perveli (18–20 October). The company lost two thirds of its strength, but did not retreat from their positions and aided the efforts of Third Army to hold the Cobadin position.
The threat from the sea, however, persisted, and on 13 December, three Russian ships attacked Balchik. Against highly unfavourable power balance, the actions of the two-gun battery commanded by Capt. Georgi Radkov, combined with raids from hydroplanes and the intervention of the first Bulgarian submarine UB 18, prevented the total destruction of the town.
The victories in Dobrudzha and the active naval defence not only granted a superiority over the enemy, but also confirmed the role of the Bulgarian armed forces as a decisive factor in the war operations on the Balkans in the hot 1916.