Edward Rydz was born in the village of Łapszyn near Berezhany, Galicia, Austria-Hungary. He was the son of a professional NCO in the Austro-Hungarian Army, Tomasz Rydz, and Maria Babiak. The family endured rather humble circumstances and he was orphaned at the age of 13 years. He was then raised by his maternal grandparents and, after their deaths, by the family of Dr. Uranowicz, the town physician at Brzeżany. After graduating with distinction at the local Gymnasium Rydz went to Kraków where he completed studies in philosophy and history of art at the Jagiellonian University. He then studied to be a painter at the arts academy in Kraków, and later in Vienna and Munich. In 1910-1911 he attended the reserve officers' academy in Vienna, and received military training at the famous Austrian 4th Infantry Regiment "Deutschmeister" (so called after Archduke Eugene, a cousin of Emperor Franz Joseph I, who was Grand Master of the Teutonic Order).
He finished his military education with distinction and was offered a commission in the Imperial Army, which he declined. In 1912 Rydz was one of the founders of the Polish paramilitary organisation Riflemen's Association (Związek Strzelecki). At the same time he completed his art studies. He was regarded as a very promising talent in landscape and portrait painting, and praised by his professors and critics, who foresaw a great future for him.
Drafted into the Austrian Army in July 1914, Rydz was transferred in August to the Polish Legions and fought in World War I in the famous Polish 1st Brigade of Piłsudski. He took part in many battles against the Russians in the region of Southern Vistula, and rose quickly in rank. By 1916, he was already a full colonel. However he did not forget his art and exhibited his work at a gallery in Kraków. In 1917, after refusing to swear an oath to the Austrian and German authorities, the Legions were disbanded, their soldiers interned and Piłsudski imprisoned in Magdeburg fortress. By Piłsudski's appointment, Rydz (who escaped prison on the grounds of bad health) became commander of Polish Military Organization (POW) and adopted the nom de guerre Śmigły (Fast or Agile), which he later added as an integral part to his surname.
In October 1918 Rydz entered the socialist government of Ignacy Daszyński in Lublin as Minister of War. Having been promoted to brigadier general (the equivalent one-star general in the Polish army), he emphasised that he had accepted the office as a deputee of Piłsudski. It was at this time he began using the double-barrelled name of Rydz-Śmigły. On November 11, 1918 the Government relinquished all power to Piłsudski, who became Provisional Head of State. After some hesitation, Piłsudski (who was displeased by Rydz-Śmigły's cooperation with the socialists - he himself "having left the streetcar of Socialism at the stop called Independence") confirmed him as a brigadier.
During the Polish-Soviet War (1919 – 1921), Rydz commanded Polish armies in several offensives. Among the victorious engagements, he captured Wilno and Dünaburg. After that, he was appointed Commander-in-Chief of the Latvian armed forces, and liberated Livonia from Red Army oppression. Subsequently, he completely annihilated the Red Army's 12th Division and took Kiev. He then commanded the Central Front of Polish forces during the Battle of Warsaw, known as the Miracle on the Vistula. In this decisive battle, Polish commander Józef Piłsudski outwitted the Soviet commander Mikhail Tukhachevsky. Rydz-Śmigły's Central Front held against the Soviet attack, and later blocked the escape routes for the defeated 4th and 15th Armies and the 3rd Cavalry Corps of Soviet General Gayk Bzhishkyan, which had to fly ungloriously to East Prussia, where they were interned by the Germans.
After the 1919-21 war he was appointed the Inspector-General of the Polish Army in the Vilna district and later in Warsaw. In 1926, during Piłsudski's coup d'état (the May Coup), he took the Marshal's side and sent troops from Wilno to reinforce anti-government troops in Warsaw. Piłsudski never forgot this fidelity and in 1929 Rydz was appointed as the Marshal's deputy on all matters concerning the East. On May 13, 1935, following Piłsudski's death, Rydz was nominated by the president and the government of Poland to serve in the capacity of the Inspector-General of the Polish Armed Forces (the highest Polish military office). This was done in accordance with Piłsudski's wishes. Piłsudski's death saw his followers (the Sanacja), divide themselves into three main factions: those supporting President Ignacy Mościcki as Piłsudski's successor, those supporting Rydz, and those supporting prime minister Walery Sławek. With a view to eliminating Slawek from the game, Mościcki concuded a power-sharing agreement with Rydz-Śmigły, which saw Slawek marginalised as a serious political player by the end of the year. As a result of this agreement, Rydz-Śmigły was to become the de facto leader of Poland, until the outbreak of the war, whilst Mościcki remained influential through continuing in the highest office of president. From 1935, Rydz saw himself rapidly elevated in rank and position. On the 15 July 1936 he was officially awarded the title of "Second Man in the State after the President", by the Polish prime minister. On November 10, he was promoted to the rank of Marshal of Poland. Rydz's image as Piłsudski's anointed successor was popularized by the Obóz Zjednoczenia Narodowego movement, but alienated many of Piłsudski's supporters, offended by what they saw as Rydz's acts of self-promotion.
The period of Rydz's rule, 1935-39, was often referred to as "a dictatorship without a dictator". Rydz lacked the moral authority of Piłsudski, and the piłsudskites were bitterly divided after 1935. The ruling regime was divided between the Mościski faction (known as the 'president's men' or the 'castle group'), made up mainly of civilians, and Rydz's group, known as the 'Marshal's Men', made up mostly of old comrades of Piłsudski and professional officers. Besides these two major groups, were the supporters of Slawek and other disgruntled piłsudskite groups, which were deprived of influence following the Rydz-Mościcki pact.
The regime became increasingly authoritarian and conservative. This was exemplified by the creation of the Obóz Zjednoczenia Narodowego (Ozon) movement. Ozon never achieved its goal of developing into a popular mass movement, and transforming Rydz into "Poland's second great leader" (after Piłsudski himself). Several of Poland's powerful politicians, including foreign minister, Józef Beck, and Mościcki himself, made a point of distancing themselves from this movement.
In March 1939, Hitler occupied Bohemia and Moravia and created the satellite client-state of Slovakia. This encircled Poland with an iron ring on all sides except the east. Rydz was the only member of the government who clearly saw the impending danger of a conflict with Germany. However, time remaining was too short for the creation of completely new Polish operation plans in the west. During negotiations in Moscow during August 1939, Rydz refused all attempts by the Western Powers to obtain Polish permission for the Red Army to march westward, stating: "there is no guarantee that the Soviets will really take active part in the war; furthermore, once having entered Polish territory, they will never leave it".