The Second World War brought complete destruction to the building; in September 1939 it was targeted and ignited by Luftwaffe fighter aircraft, and then detonated by the Nazis after the failed Warsaw Uprising in 1944.

In 1965, the surviving wall fragments, cellars, the adjacent Copper-Roof Palace and the Kubicki Arcades were registered as historical monuments.

In the early 1600s, it was designated to replace Wawel Castle in Kraków as the seat of the king, Parliament (Chamber of Deputies and Senate), and the Polish–Lithuanian Commonwealth.

In 1339, the Papal Legate in Warsaw[5] heard a case brought by the King of Poland, Casimir III the Great, against the German Teutonic Order.

At that time a fortified town surrounded by earthen and wooden ramparts, and situated where the Royal Castle now stands, it was the seat of Trojden, duke of Masovia.

At the end of the 13th century, during the Duke Conrad's rule, the wooden-earthen gord called "Small Manor" (Latin: Curia Minor) was erected.

[7] Following the Lublin Union (1569), by which the Polish Crown and the Grand Duchy of Lithuania – were united as a single country, Warsaw Castle was regularly the place where the parliament of the Two-Nations State met.

[6] In 1569–1572, King Sigismund II Augustus started alterations in the castle, the architects being Giovanni Battista di Quadro[8] and Giacopo Pario.

[6] The parliamentary character of the Curia Maior is stressed by the paintings of the facade – the coats-of-arms of Poland, of Lithuania, and of the various regions from which the delegates were elected.

Later after 1614, when Matteo Castelli[9] took the lead, the western wing was built (from today's Plac Zamkowy side) as chancelleries and a marshals office.

On 29 October 1611 in the Senator's Chamber, Tsar Vasili IV of Russia, who had been captured by the hetman Stanisław Żółkiewski, paid homage to the Polish king Sigismund III Vasa.

Sigismund III and his successors of the Vasa dynasty — Władysław IV Vasa and John II Casimir Vasa — collected many rich works of art in the castle, such as oriental fabrics, tapestries, and numerous paintings by such famous artists as Titian, Veronese, Jacopo and Leandro Bassano, Tintoretto, Palma il Giovane, Antonio Vassilacchi, Tommaso Dolabella, Guercino,[11] Guido Reni,[11] Joseph Heintz the Elder,[11] Bartholomeus Spranger,[11] Roelant Savery,[11] Rembrandt,[11] Pieter Soutman, Peter Danckerts de Rij, Peter Paul Rubens,[11] Jan Brueghel the Elder,[11] Daniel Seghers, Georg Daniel Schultz and sculptures by Giambologna, Giovanni Francesco Susini and Adriaen de Vries.

The great opera hall (double-storied, over 50 m long), which existed at the Royal Castle,[9] was demolished by Swedes and Germans and rebuilt in the 1660s by King John II Casimir.

[14] On 25 May 1702 the Swedes re-seized the Royal Castle in Warsaw, creating a hospital with 500 beds, and into the Chamber of Deputies and ministers' rooms, they placed a stable.

[14] In 1707, by virtue of the peace treaty between Augustus II and Charles XII of Sweden, Russian allied troops entered Warsaw, and Tsar Peter I of Russia settled in the castle.

During the following years, between 1722 and 1723, the other castle halls were converted-under the direction of architect Joachim Daniel von Jauch, the new Senate Chamber was built, and all the furnishings moved from the old to the new location, including among others: 60 Polish provincial emblems, panelling, mouldings and lesene.

[14] On 31 May 1732, a fire broke out in the castle destroying the west elevation and part of the Sigismund's Tower and the exterior façade sculptures, known as armature.

During the period of 1740–1747, the façade on the Vistula side was reconstructed in the late baroque style (architects: Gaetano Chiaveri, Carl Friedrich Pöppelmann, Jan Krzysztof Knöffel).

The last reconstruction work of this period was finished by late 1763, after the death of Augustus III, when Plersch made the last sculptures and frames with province emblems for the Parliament Hall.

During 1766–1785 on the basis of Jakub Fontana's plans,[7] the southern wing of the castle, which was burnt on 15 December 1767 was rebuilt (2 destroyed floors, a new elevation on the south side with three avant-corps or risalti, the division of the façade by lesene and pilasters with Ionic capitals).

[8] These rooms contained pictures and sculptures depicting great events in Poland's history, as well as portraits of Polish kings, generals, statesmen and scholars (including Copernicus and Adam Naruszewicz).

Here in 1807 he made the decision to form the Duchy of Warsaw, which was to be ruled by the Saxon king Frederick August I, using the Royal Castle as his residence.

Prince Józef Poniatowski, Commander-in-Chief of the Army of the Duchy of Warsaw and Marshal of France, resided in the Copper-Roof Palace joined to the castle.

Paskievich charged Ludvik Corio – a Russian Colonel and architect – with designing new elevations and façades (the west, south, and east parts).

In 1890, the Saxon Elevation was rebuilt under the supervision of a builder January Kiślański, when the arcades of both viewing galleries, dating back to the Augustus III period, were deformed.

On one of these fragments part of the stucco decoration remained, this was a cartouche with the royal version of the motto of the Order of the White Eagle — "PRO FIDE, LEGE ET REGE" (for Faith, Law, and King).

This huge clock tower (60 metres (200 ft) in height), designed in the 17th century, has always been a symbol of the Polish capital and source of inspiration for the architects of other buildings in Warsaw.

[25] In December 2018, a painting by Marcello Bacciarelli titled Portrait of Jerzy Mniszech with Daughter Elizabeth and Kiopek (1795), which was considered missing, was returned to the castle's collections.

[33] In 1979, the historic Gateway Theatre in the Jefferson Park community area of Chicago was purchased by the Copernicus Foundation with the intention of converting it into the seat of the Polish Cultural and Civic Center.

Because of the building's historical significance, its interior was kept intact while the exterior was remodelled and a Neo-Baroque clock tower was added to give it the resemblance of the Royal Castle in Warsaw.