Compenstaion for combatants during raashidoon

In present day we see people working in the army, are paid fixed salaries. My question is were the combatants during reign of 4 rightly guided caliphs paid any renumeration besides spoils of war. I'm asking this because, if we read the biographies of prophet and companions we see moderate to perfect altruism, same can be said about combatants if the only source of income is spoils of war. And at times muslims didnt win battles, which will result in no gain in spoils. Searching the internet is yielding results, that they were paid once a year in Muharram, without any source and no information is provided if a person is forced to return before muharram.