It depends on the scenario, not all alliances are good and not all are bad.
Chat with our AI personalities
GOOD
there there for you and they help you out when you need it
BAD
they may not really be on your side they can just be pretending
All of these answers are good ones. Alliances are made for support.
Secret alliances
Nations making political and military alliances was an effect of militarism.
Alliances have always been a part of European politics. Initially between church and state, but as countries became more independent, alliances were formed between them. Alliances are always formed for the same reason, to achieve a "balance of power" whether it be military or economic.
In WW I the two major alliances were the Allies (or Allied Forces) and the Central Powers.