During the initial period of VOC settlement, accommodation requirements were simple and pragmatic. Fortified trading stations were built according to  the rules of military architecture. In addition sufficient building space for merchants and their commercial administration, warehouses to store  merchandise, a church, a hospital and of course housing for military garrison, including a munitions store, were required.
4). Passchier, Cor, The Past in The Present Architecture in Indonesia

zelfstandig, gesloten en naar alle zijden verdedingbaar werk; heeft als regel geen burgerbevolking. Opmerking: onderscheiden kunnen worden: eenheidsfort, gebastioneerd fort, gedetacheerd fort, kustfort, pantserfort, polygonaal fort, positiefort, sperfort en torenfort.4)
5). Stichting Menno Van Coehoorn, Terminologie Verdedigingswerken,1999.

The definitions of forts are a military construction or a structure built for defense purposes, usually consists of high walls, or enforced/strong earth. Included here are walls built to protect a city from hostile acts. Sometimes forts are supplemented with trenches dug around it. Aside for defensive purposes, forts are often used as dwelling or the boundary of a city. Humans have constructed defensive works for many thousands of years, in a variety of increasingly complex designs. The term is derived from the Latin fortis ("strong") and facere ("to make").
6).www.en.wikipedia.org

A strong or fortified place; especially : a fortified place occupied only by troops and surrounded with such works as a ditch, rampart, and parapet :  A permanent army post —often used in place names
7).merriam webster online dictionary

In military science, any work erected to strengthen a position against attack. Fortifications are usually of two types: permanent and field. Permanent fortifications include elaborate forts and troop shelters and are most often erected in times of peace or upon threat of war. Field fortifications, which are constructed when in contact with an enemy or when contact is imminent, consist of entrenched positions for personnel and crew-served weapons, cleared fields of fire, and obstacles such as explosive mines, barbed-wire entanglements, felled trees, and antitank ditches.
6).www.en.wikipedia.org

Looking at Stevin’s Ideal Scheme for a City several typical Dutch features strike the eye, revealing the reason why the scheme is known as ‘the Dutch urban mode;’. In essence, Stevin’s ground plan shows similarities with a Roman army (a title he had chosen for himself) he had made through studies of the Roman art of war. In Castrametatio,p.372 of volume IV : the Art of War’, he publishes a ground plan of an army encampment, already revealing elements which are very similar to his later “ideal Scheme for a City”. A rectangular area enclosed by a fortification wall, with bastions at regular intervals. These bastions were an element added and worked out by Stevin and explained systematicaly for the first time in his treatise Stercktenbouwing (The Art of Fortification) of 1594, which would associate his name. ‘before all others with the so called Old Dutch method of Fortification. [...] In Chapter V [of this treatise] he demonstrates with the aid of illustrations how this most important element of the system, the bastion, came into being.’

The definitions of forts are a military construction or a structure built for defense purposes, usually consists of high walls, or enforced/strong earth. Included here are walls built to protect a city from hostile acts. Sometimes forts are supplemented with trenches dug around it. Aside for defensive purposes, forts are often used as dwelling or the boundary of a city. Humans have constructed defensive works for many thousands of years, in a variety of increasingly complex designs. The term is derived from the Latin fortis ("strong") and facere ("to make").

The two bastions at each corner extend slightly outside the line of the fortifications to provide a better vision on the surrounding countryside and along the length of the wall. The settlement has two distinct axes at right angles of each other, in Roman times one running precisely north south and the other east west, respectively called Cardo and Decumanus, with gates at the end of each axis. Stevin re-arranged this ground plan with ‘defensive, capitalistic and secular elements of planning’, all explained hereafter, according to the latest Renaissance principles, by a formal network of perpendicular streets with central points and rigid social distinctions-an image set by the aristocratic character of Holland at that time, according to Greig. Added to this are features typical of the Low Countries, like the traditional use of water for defence, management, communications and leisure.

The first typical Dutch element is the surrounding water-filled moat or wet ditch, together with the canals that intersect the total gound plan. The central canal (or river) forms the premier, longitudinal axis of the settlement.

‘before all others with the so called Old Dutch method of Fortification. [...] In Chapter V [of this treatise] he demonstrates with the aid of illustrations how this most important element of the system, the bastion, came into being. 7)
7). Van Oers, Ron, Dutch Town Planning Overseas During VOC and WIC Rule (1600-1800), 2000

The definitions of forts are a military construction or a structure built for defense purposes, usually consists of high walls, or enforced/strong earth. Included here are walls built to protect a city from hostile acts. Sometimes forts are supplemented with trenches dug around it. Aside for defensive purposes, forts are often used as dwelling or the boundary of a city. Humans have constructed defensive works for many thousands of years, in a variety of increasingly complex designs. The term is derived from the Latin fortis ("strong") and facere ("to make").
6).www.en.wikipedia.org

Larger forts may class as fortresses.
6).www.en.wikipedia.org