Indeed, that has seen Pompey recruit 11 new faces this window including the impressive captures of Colby Bishop, Marlon Pack and Dane Scarlett.
The Blues aren’t finished there either with a winger, central defender and striker still believed to be on Cowley’s wishlist before deadline day.
Promotion rivals including Derby, Sheffield Wednesday, Ipswich and Co have also splashed the cash as they put in a bid to win promotion back to the Championship.
With next Thursday marking the closure of the transfer window, we’ve taken a look at the top 15 most impressive signings made by League One clubs this summer.
Here’s who we think made that list.
1. Jesurun Rak-Sakyi - Charlton
The highly-rated winger impressed under Patrick Viera in the Crystal Palace first-team during pre-season. The 19-year-old was given his first loan spell away from Selhurst Park to their London rivals Charlton, with the youngster penning a season-long stay. Rak-Sakyi netted on his debut and has made three outings to date. Photo: Will Russell
2. Freddie Ladapo - Ipswich
The want-away striker finally got his move away from Rotherham this summer as he made a free switch to Ipswich. The prolific goalscorer netted 15 times in 41 outings for the Millers last term but is yet to open his account for the Tractor Boys after signing a three-year deal in May. Photo: Alex Pantling
3. Dane Scarlett - Pompey
Scarlett is tipped to become one of the most exciting up-and-coming youngsters in English football after impressing at academy level for Spurs. The 18-year-old played a key role in England’s success in this summer’s under-19 Euro’s prior to his switch to Pompey. The striker signed a season-long loan at Fratton Park in July but is yet to score his first goal for the Blues. Photo: Malcolm Bryce
4. Conor Hourihane - Derby
The former Republic of Ireland intentional was playing Premier League football under two years ago before making the drop to League One. Hourihane arrived at Pride Park in July, where he signed a two-year deal with the Rams. The midfielder has since scored one goal in seven outings following his free move from Sheffield United. Photo: Malcolm Couzens