May the peace, mercy and blessing of Allah be upon you.

Is it permissible to pray outside of the masjid (in a park, for example, or on public streets wearing shoes)? Also, is this permissible in a state of war?

May Allah reward you.

In the Name of Allah, the Beneficent, the Merciful,

All praise is due to Allah, and may peace and blessing be upon the Messenger of Allah, upon his household, his companions and whoever follows him. To proceed:

There is nothing wrong with praying outside the masjid if the rows are connected, the person praying outside can follow the imam and there is some need for that, like crowding or the like. There is also nothing wrong with praying in shoes, whether inside the masjid or outside, whether in times of war or peace, as long as one doesn't know of any impurity on them and as long as that does not result in ruining the carpets, soiling them or the like. This is according to the saying of the Prophet (saws), "Verily, the Jews do not pray in their shoes, so differ from them and pray in your shoes." However, the masajid in the time of the Prophet (saws) were not carpeted. Therefore, anyone praying in his shoes now, after the masajid have been spread with carpets, should make sure that they are clean so as not to ruin the carpeting or soil it. If his shoes are not clean, it would be better to take them off since that would result in money being wasted and carpets being soiled needlessly.