The offer was triggered by an agreement between Kroenke's company, KSE, and DF Nominees (the company holding Danny Fiszman's interests in Arsenal Shares) whereby KSE will have the right to buy DF Nominee's 16.11% stake within 20 days of Fiszman's death. Along with KSE's 29.9% holding, that agreement effectively gave the US group control of more than 30% of Arsenal shares - which means it is compelled to make an offer to all Arsenal shareholders under the Takeover Code (Rule 9). Separately, KSE has agreed to acquire Lady Nina Bracewell-Smith 16.79% stake, plus smaller shareholdings of Arsenal directors. In total KSE now speaks for 62.89% of Arsenal shares.
KSE now has four weeks to launch its offer to other Arsenal shareholders - which will involve it sending out formal documents to shareholders. This offer must stay open for a minimum of 21 days, but can run for three months.
Once the shareholders have received the offer, they can either accept or decline it. In order for the Arsenal shares to be de-listed from Plus Markets - the junior stock exchange on which they are traded - KSE will need to control more than 75% of the shares. Even if the company got above 75%, that does not necessarily mean that the shares will be de-listed - for example if there are substantial numbers of independent shareholders who still want to hold their shares in a public company there could be a case where these shares are still traded on the stock market. However, even if the shares remained traded on Plus, KSE would have control of the company - and therefore the club.
KSE says that if it acquires more than 90% of Arsenal shares (which would mean it had bought Alisher Usmanov's 27% stake) it might consider a compulsory purchase of any remaining shares - meaning that Arsenal shareholders who had refused to sell will have no choice but to cash in their holding.