A major port, agricultural, trade and shipbuilding centre for the Ottoman Empire in the 16th – 17th century, preserving a significant and economically active Bulgarian population, Varna was later made one of the Quadrilateral Fortresses ( along with Rousse, Shumen, and Silistra ) severing Dobruja from the rest of Bulgaria and containing Russia in the Russo-Turkish wars.

However, the Austrians themselves generally had little interest in the region ( aside from a short-lived attempt by Emperor Charles VI to compete with British and Dutch trade through the Ostend Company ), and the fortresses along the border ( the Barrier Fortresses ) were, by treaty, garrisoned with Dutch troops.

Fortresses along those walls and further up and down the coast from the city were modernized, and the Arsenale — the naval shipyards — were expanded considerably.

Although Rasuwa Gadhi and Duguna Gadhi Fortresses were not constructed at the time, the places themselves were important because of their military significance.

Fortresses built in this style throughout the 16th century did not become fully obsolete until the 19th century, and were still in use throughout World War I ( though modified for 20th century warfare ).

Fortresses were built, although used temporarily.

During the morning of 24 June, 74 American B-17 Flying Fortresses were again dispatched to the bridge ; 38 hit the primary and 36 hit Tours / La Riche Airfield without loss ; escort was provided by 121 of 135 P-51s.

Built in murus dacicus style, the six Dacian Fortresses of the Orăștie Mountains, in Romania, were created in the 1st centuries BC and AD as protection against Roman conquest.

When 14 surviving B-17 Flying Fortresses and 143 personnel of the heavy bombardment force were withdrawn from Mindanao to Darwin, Australia in the third week of December 1941, Headquarters FEAF followed it within days.

The 14th and 28th Bomb Squadrons ( the latter a longtime part of the 4th Composite Group, which disbanded on 16 November 1941 ) were attached to the 19th BG and a total of 35 B-17 Flying Fortresses constituted the FEAF's heavy bombardment force.

Although 38 of the more capable B-17E Flying Fortresses and a dozen LB-30 Liberators incrementally reinforced the FEAF, losses were severe and the slow rate of reinforcement was unable to keep pace.

On the morning of December 6, 1941, two squadrons of 19th Bombardment Group B-17 Flying Fortresses stationed at Clark ( 16 of its 35 bombers ) were sent down to Del Monte No. 1, just completed the day before, although no maintenance facilities existed and the materiel to support them was not scheduled to be moved until December 10.

Fortresses were built and an alliance was formed with nearby native Tupi-Guaraní tribes to defend the settlement against other European invaders.

Ratweek, started on 1 September 1944, also involved the Navy and the Partisans USAAF Flying Fortresses ( 50 ) were called in to bomb Leskovac and impede the German withdrawal, though with many civilian casualties

By the late 1940s, the B-17 Flying Fortresses and B-24 Liberators used in the European Theater of the war were thoroughly obsolete as combat aircraft and were mostly sent to the smelters.

Of the 291 B-17 Flying Fortresses sent on the mission, 60 were lost outright, another 17 damaged so heavily that they had to be scrapped, and another 121 had varying degrees of battle damage.

Eight B-17 Flying Fortresses were sent to the location but failed to locate the ships.

Badly-damaged Fortresses were often instructed to crash land at Honington on return from operations, particularly if their landing gear could not be lowered, as this avoided the necessity to dismantle and transport the aircraft from its home base for repair.

Casey Jones flights were made by RB-24 Liberators and RB-17 Flying Fortresses converted for photographic use.

No 100 Group operated from eight airfields with approximately 260 aircraft, 140 of which were various marks of Mosquito night fighter intruders with the remainder consisting of Halifaxes, Stirlings, Wellingtons, Fortresses and Liberators carrying electronic jamming equipment.

Their guns tended to freeze at high altitude and were generally unable to effectively protect the Fortresses.

Various armament configurations of two to four flexible guns were utilized in the field, but the problem was not adequately addressed until the introduction of a powered, remotely operated " chin " turret in the final production blocks of the F-series Fortresses, directly derived from its debut on the YB-40 experimental " gunship " version.

As the Reconquista spread throughout Spain, many Mosques and Fortresses were converted into Churches and Christian Castles.

" Already the Fortresses were over their target -- were past it -- when, as we watched, the whole of Leskovac seemed to rise bodily into the air in a tornado of dust and smoke and debris, and a great rending noise fell on our ears.

When the evacuation party arrived by PT boat from Corregidor on March 16, four B-17 Flying Fortresses from Australia flew up to Del Monte: B-17E 41-2408, B-17E 41-2429, B-17E 41-2434 and B-17E 41-2447 and evacuated them to Batchelor Field.

The bookseller and publisher Zedler published this book in Leipzig under the name " Great Complete Encyclopaedia of All Sciences and Arts Which So Far Have Been Invented and Improved by Human Mind and Wit: Including the Geographical and Political Description of the Whole World According to All Monarchies, Empires, Kingdoms, Principalities, Republics, Free Sovereignties, Countries, Towns, Sea Harbors, Fortresses, Castles, Areas, Authorities, Monasteries, Mountains, Passes, Woods, Seas, Lakes ... and also a Detailed Historical and Genealogical Description of the World's Brightest and Most Famous Family Lines, the Life and Deeds of the Emperors, Kings, Electors and Princes, Great Heroes, Ministers of State, War Leaders ... ; Equally about All Policies of State, War and Law and Budgetary Business of the Nobility and the Bourgeois, Merchants, Traders, Arts.

This Fortresses was constructed ny Denmark-Norway in the 17th century as a replacement for the border fortress at Bohus, which had been lost when the province of Bohuslän was ceded to Sweden by the terms of the Treaty of Roskilde in 1658.

* January 17 – The United States Army Air Corps orders 13 Boeing Y1B-17 Flying Fortresses, previously known by the manufacturer's designation, Model 299.

* March 2 – The Allied air forces make their largest attacks of the Anzio campaign, with 241 B-24 Liberators and 100 B-17 Flying Fortresses escorted by 113 P-38 Lightnings and 63 P-47 Thunderbolts dropping thousands of fragmentation bombs around Castello di Cisterna, Velletri, and Carroceto, Italy.

Although initially adapted for the Warwick, the lifeboat was subsequently also carried by Air-Sea Rescue Lancasters and B-17 Flying Fortresses.

The fort was ordered under the auspices of the 1859 / 60 Royal Commission on the Defences of the United Kingdom, but it was deleted by Parliament in an attempt to save money and divert funds to the construction of the sea forts, and the Land Front Forts of Milford Haven, Plymouth, Cork and Portsmouth / Isle of Wight Fortresses.

However, enclosed in its own pressurised container, ( to prevent arcing of the high voltages inside ), it was large and at 600 lb took up the entirety of the bomb bay of the Boeing Fortresses used by No. 100 Group RAF.

" A Third Intermediate Period text mentions there being at least five " Fortresses of the Meshwesh " in the area of Herakleopolis Magna ; these were probably the ones established by Ramesses.

With the departure of the 15th Bomb Squadron, Molesworth was occupied by the B-17 Flying Fortresses of the 358th Bombardment Squadron, the first of four squadrons that would comprise the 303d Bombardment Group.

The Dutch, however, who had supplied the major share of the troops and money to secure the victory ( the Austrians had produced nothing of either ) claimed the government of the region till the war was over, and that after the peace they should continue to garrison Barrier Fortresses stronger than those which had fallen so easily to Louis XIV ’ s forces in 1701.

This included 2, 600 Venturas, 2, 750 B-17 Flying Fortresses ( built under license from Boeing ), 2, 900 Hudsons, and 9, 000 Lightnings.

The military activities in Stavern began with building of Staverns Fortress, part of a major construction of Norwegian Fortresses which took place from 1675 to 1679 under Christian IV.

There are less than 2 or possibly more fortifications and 6 or more coastal defensive positions commanded from Itarkioi and Ketoebone Fortresses.

* February 15 – 27 – Six United States Army Air Corps B-17 Flying Fortresses make a goodwill tour of Latin America, traveling from the United States to Lima, Peru ; Buenos Aires, Argentina ; Santiago, Chile ; and back to the United States.

The plant turned out some 1, 000 A-20 Havocs, not to mention 3, 000 B-17 Flying Fortresses and 1, 156 A-26 Invaders.

** 131 U. S. Army Air Forces B-17 Flying Fortresses conduct a bombing raid against the headquarters of Field Marshal Albert Kesselring at Frascati, Italy, killing 485 civilians.