On 10 October, with the end of the attempted breakthrough the Bulgarian High Command ordered the 1/3 Brigade to be returned to the 3rd Balkan Infantry Division.

Until the first armistice was concluded the Second Army limited its operations to tightening the encirclement and shelling the fortress in order to reduce the morale of its defenders.

As soon as it became evident that the Ottomans were not willing to satisfy the demands of the Balkan League, the Bulgarian High Command began preparing for a possible renewal of the military operations and drawing plans for the capture of the Adrianople Fortress.

On 26 January the Ottomans began a large offensive against Bulair and on the Çatalca line in order to break through the Bulgarian armies and relieve the forces in Adrianople.

After three days of heavy fighting the fortress fell and Sukru Pasha surrendered to generals Nikola Ivanov and Georgi Vazov.

Its composition had changed significantly and now included two half-strength divisions and three infantry brigades, two of which had been recently raised from young untrained and inexperienced men from the territories ceded by the Ottoman Empire.

The Army remained dispersed on a 96-kilometer-long front which severely hampered the coordination and cooperation between its forces, leaving general Ivanov with no reserves.

The numerical superiority of the Greeks and their artillery proved decisive and on 26 June they took Strumitsa outflanking the Bulgarians at Ruppel and forcing their retreat.

The Serbians and the Greeks now established direct contact with each other and planned a joint offensive, hoping to link up at Tsarevo Selo and destroy the Bulgarian 4th and 2nd armies.

The Bulgarian Second Army was in no condition to hold the Greek advance as it had suffered heavy casualties in the previous battles and a cholera outbreak further reduced its strength.

The advance was to continue on 18 July but the Greek king managed to obtained the ceasefire he and the Bulgarian delegation in Bucharest desired before any further military actions were undertaken.

The Serbians adopted a passive defense approach, hoping that their insufficient forces will hold out long enough for the Entente to reinforce them with the troops that were already landing in Salonika.

On 10 October concerned by the Serbian and Entente efforts to join their forces in Macedonia from the North and the South, the Bulgarian High Command divided the Second Army in two operational groups.

After the fall of Pristina and Prizren the Bulgarian High Command again turned its attention to the south and began transferring reinforcements for operations against the Entente forces that had grown to as much as 130,000 men.

By December the Bulgarian Second Army undertook a major offensive against the retreating allies and after several engagements with the French and British 10th (Irish) Division at Kosturino reached the Greek border.

At this point Vardar Macedonia was completely cleared of Entente presence but the Second Army several times received warnings from the Bulgarian High Command that any crossing of the Greek border was absolutely forbidden.

The Bulgarian High Command realized that if the Entente occupied the Southern exit of the Ruppel Pass and took the fortress there, the Second Army would not be able to advance south along the Struma and the threat of an Allied attempt to penetrate into Bulgaria itself would grow significantly.

The Bulgarian High Command realized the difficulties involved in holding such a long front and planned measures to improve the situation.

The expected entry of Romania in the war on the side of the Entente provided an additional incentive and an eventual German blessing for a Bulgarian offensive on the Macedonian front.

The plan was to strike on both Allied flanks in order to cut their communication lines with the Italians in Albania and seize the Drama – Giumurdzhina railway.

Most importantly, however, the Macedonian front was shortened with 100–120 kilometers and the Greek IV Army Corps, that was positioned in the area, was disbanded, its troops and armament interned by the Germans in Silesia.

After 4 October the Bulgarians set up positions on the nearby heights to the east while the right flank of the 7th Rila division remained in the valley to protect the Rupel Pass.

In the middle of October and the beginning of November, the Bulgarians were reinforced by two Ottoman divisions which freed some troops that could now be sent to assist in the fighting against the Allies west of the Vardar.

Nonetheless, the army continued to hold the Struma line and foiled a Greek attempt to capture Serres, gaining a few cannons as trophies.

Throughout 1940 and 1941, the Kingdom of Bulgaria, under Tsar Boris III, allied itself with Adolf Hitler's Germany, entered the regained Southern Dobrudja, and captured Thrace, and much of Macedonia in the process.

In an attempt to prevent the entry of the Red Army in the country on 26 August, the government of Ivan Bagryanov declared Bulgarian neutrality in the German-Soviet war.

Three days later the new government of Konstantin Muraviev declared war on Germany in vain as the Red Army entered the country and soon the prime minister was overthrown and replaced with the Fatherland Front's government which immediately concluded a ceasefire with the Soviets and prepared the Bulgarian Army for operations against the forces of Germany.

The Bulgarians, placed under the battle order of the 3rd Ukrainian Front, were tasked with advancing in three directions – Sofia to Niš to Pristina, Kyustendil to Skopje, and Blagoevgrad to Veles.

In the area around the village of Meroshina the Bulgarians defeated the main forces of the 7th SS Volunteer Mountain Division Prinz Eugen allowing the Army to complete its objectives by reaching Podujevo and preparing for further offensive actions.

The advance was hampered by the strong German resistance and the onset of Winter, but the Bulgarians managed to capture Pristina on 19 November and enter Kosovo with their main forces.