As mandated by FIFA regulations, the transfer window is the registration period during which clubs can transfer players from other teams into their own.
For most major European leagues (which start around August - September, and end in May, there are two such windows, the longer one between the end of a season and the commencement of the next one, and the shorter one in the middle of the season.
Usually, the summer transfer window is a period of busy activity for major European clubs. The summer transfer window in 2019-20, which closed on 2nd September 2019 in Italy, Spain, Germany, and France (the English window closed on 8th August 2019), was no different and saw a spate of high profile transfers in European club football.
English clubs were the busiest during this period, leading the way with €1.54 billion (£1.4 billion). Juventus, Napoli, Roma, and the two Milan clubs shelled out a combined €690 million while in the Bundesliga, Bayern and Dortmund got poorer by €271 million.
The top-three clubs in Spain (Real Madrid, Barcelona, and Atletico) hauled in summer reinforcements for a combined €806 million. Real Madrid had the most transfer outflow (€307.5 million) for a club during this period.
Midfielders were the flavour of the summer, with the top 25 transfers during this period involving 10 midfielders. Here is a preview of the 10 most expensive summer acquisitions of the season, which features an eclectic ensemble of three strikers, four midfielders, and three defenders:
#10 Romelu Lukaku (€65 million)
Romelu Lukaku moved from Manchester United to Serie A club Internazionale for 65 million Euros. The 26-year-old Belgian centre-forward arrives in Italy after scoring 33 goals in the Belgian League (Anderlecht) and 113 goals in 9 seasons in the English Premier League (Everton-68, Manchester United-28, and West Ham-17).
Inter were scouting for a reliable striking option after protracted contract negotiations with their erstwhile captain Mauro Icardi who fell out of favour with the club faithful and eventually joined PSG on a loan deal. In Lukaku, Inter seems to have found a like-for-like replacement as the Belgian announced his arrival in Italy with goal scoring debut.
#9 Rodrigo Hernández (€70 million)
Rodrigo Hernández, also known as Rodri, is the third-most-expensive acquisition by a Premier League club this summer. Manchester City triggered Rodri's release clause by shelling out a club-record €70 million (£62.8 million) to Atlético Madrid.
The 23-year-old Spanish defensive midfielder arrives in England after four seasons in the Primera Liga (3 seasons with Villareal and 1 season with Atlético).