They fell one point short of promotion to the old Division One. Millwall's most famous stadium became The Den at New Cross (London) where they moved in 1910. The Den cost about £10,000. Millwall reached the final against London Caledonians. In 1978 The O's managed to reach the semi-finals of the FA Cup. The official attendance record stands at 48,762, set in the 1937 FA Cup against Derby County FC. On 7 April 1945, Millwall played in the Southern FA Cup Final at Wembley against Chelsea, but as this was an unofficial "war final", this game is nowhere recorded in the history books. Proteus Charm – The Proteus Charm allows items to take the exact shape of a main item so that it can send messages around. He allows himself to be carried by the she-wolf, who can hardly move forward. On 27 April 2019, after a goalless draw against Braintree Town, Orient secured promotion to League Two, after a two-year absence.

First under trainer Felix Schavy, a year later with Norberto Höfling at the helm. Despite losing 8-1 in the FA Cup, Millwall won the East London Senior Cup three years in a row. Millwall played in front of 25,000 supporters and beat The Red Devils 2-1. In the 1958-59 season, Millwall became a founder member of Division Four. The same is true of architecture, as practiced by Brunelleschi, Alberti Leone, Andrea Palladio and Bramante. Millwall produced some well-known players during this period, such as winger Barry Rowan and goalkeeper Alex Stepney. Furthermore, there are local rail lines to commuter towns such as Monza. Associazione Calcio Monza (AC Monza for short) is an Italian football club from the city of Monza, Lombardy and plays in the Serie A. The Northern Italian club plays its home games at the Stadio Brianteo. Before this, it played at the Stadio Sant'Elia. Millwall also has two well-known mottos: "No One Likes Us, We Don't Care" and "We Fear No Foe Where E'er We Go". Millwall lost this game 2–0, despite their favorite status. Millwall enjoyed very little success during this period and were relegated several times.

Millwall regularly attracted 40,000 supporters for a game, especially at the football ground on East Ferry Road. At its peak, the hospital had 175 beds for 2 people each. The game ended 2-2, both teams each received the cup for six months. Already after a few months, the supporters called for his resignation because of the poor results. There were about 90,000 supporters on the post, the largest crowd Millwall has ever played for. Supporters took to the pitch in the 80th minute, jamaica soccer jersey clamoring for the Italian to leave. Millwall lost 0–1. It was here that the well-known Millwall Roar was born. The Millwall fans, on the other hand, only whipped up their own team, with the famous "roar", from start to finish. Millwall set an all-time record for the club in the late 1960s with 59 home games unbeaten in a row, from 22 August 1964 to 14 January 1967. This was thanks to managers Billy Gray and Benny Fenton.

In the same season, The O's equaled the old club record by going 14 games unbeaten, but ended up just outside the playoffs for promotion to the Championship. Seven minutes after the break, Raspadori equalized and Sassuolo eventually won through a goal from Francesco Caputo. His first goal followed in a duel with RSC Anderlecht. The then 74-year-old Goethals returned one last time to temporarily help Anderlecht out of distress. In the first season, only three times was lost. Protests against owner Becchetti intensified, resulting in a pitch invasion on April 29 during the last home game of the season. The Den was bombed during the London Blitz. The Den became one of the most feared stadiums in the country, as no team liked to come and play there due to the rowdy crowd that was always there. The club plays its home games at New Den Stadium. The match between Arsenal and Man United starts on Sunday, January 22 at 5:30 PM at the Emirates Stadium (London). In 2010 Leyton Orient beat Championship club Norwich City 1-0 in the 3rd round, and Swansea in the 4th round of the FA Cup 2-1, making it to the 5th round, quite an achievement for a League One club. club, was allowed to play against Premier League giant Arsenal.